2. 1796:Edward Jenner (1749-1823)
used cowpox to vaccinate against
smallpox
was the first person to deliberately
vaccinate against any infectious disease
used a preparation to elicit an immune
response.
Variolation
– infecting people with smallpox
– to protect them from the worst type of
the disease
3. 1885: Louis Pasteur (1822-1895)
experimented with rabies
vaccination
using the term "virus" to describe
the agent
"virus" and "vaccination" (in honor
of Jenner)
4. 1886: John Buist
Scottish pathologist
stained lymph from skin lesions of a
smallpox
– "elementary bodies"
– he thought were the spores of
micrococci
– smallpox virus particles
5. 1892: Dmiti Iwanowski (1864-
1920)
described the first "filterable"
infectious agent
– tobacco mosaic virus (TMV)
smaller than any known bacteria
first to discriminate between
viruses and other infectious
agents
6. 1898: Martinus Beijerinick (1851-
1931)
– extended Iwanowski's work with
TMV
– developed the concept of the virus
as a distinct entity
7. Freidrich Loeffler (1852-1915)
and Paul Frosch (1860-1928)
– demonstrated that foot and
mouth disease
– first to prove that viruses could
infect animals as well as plants
8. 1900: Walter Reed (1851-1902)
demonstrated that yellow fever is
spread by mosquitoes
first to show that viruses could be
spread by insect vectors such as
mosquitoes
1908: Karl Landsteiner (1868-
1943) and Erwin Popper
proved that poliomyelitis: virus
proved that viruses could infect
humans as well as animals
9. 1911: Francis Peyton Rous (1879-
1970)
demonstrated that a virus (Rous
sarcoma virus) can cause cancer in
chickens
first person to show that a virus
could cause cancer
10. 1915: Frederick Twort (1877-1950)
discovered viruses infecting bacteria
1917: Felix d'Herelle (1873-1949)
– independently discovered viruses of
bacteria
– coins the term bacteriophage
11. 1938: Max Theiler (1899-1972)
developed a live attenuated vaccine
against yellow fever
safe and effective that it is still in
use today!
1940: Helmuth Ruska (1908-1973)
used an electron microscope: virus
particles
direct visualization of virions
12. 1941: George Hirst
demonstrated that influenza virus
agglutinates red blood cells
viruses could be counted
1945: Salvador Luria (1912-1991)
and Alfred Hershey (1908-1997)
demonstrated that
bacteriophages mutate
antigenic variation in viruses.
13. 1957: Alick Isaacs and Jean
Lindemann
discovered interferon
– first cytokines to be studied in
detail
Carleton Gajdusek
– proposed: a "slow virus" is
responsible for the prion disease
kuru
– kuru is similar to that of scrapie
– kuru can be transmitted to
14. 1961: Sydney Brenner, Francois
Jacob, and Matthew Meselson
demonstrated that bacteriophage
T4 uses host cell ribosomes
– to direct virus protein synthesis
– fundamental molecular
mechanism of protein translation.
15. 1963: Baruch Blumberg
discovered hepatitis B virus (HBV)
developed the first vaccine against
the HBV
– first vaccine against cancer
1989: Hepatitis C virus (HCV)
nonA, nonB hepatitis
first infectious agent to be identified
by molecular cloning of the genome
16. Sending Specimens to the
Laboratory
–Right specimen
–Taken at the right time
–Stored and transported
immediately
17. Specimens for viral isolation or Ag
detection
Respiratory Infection Nasal or throat
swabs, postnasal
washings
Gastrointestinal infxn Feces
Vesicular rash Vesicular fluid, throat
swab, feces
Hepatitis Serum, feces
CNS CSF, throat swab,
feces
AIDS Unclotted blood
25. Direct Examination
Main advantage: short
length of time required for
result
Results available the same
day
specific antiviral
chemotherapy
26. Direct Examination
Automated molecular
biology techniques
available:
1. PCR-based amplicor
system
2. Abbott LCR system
3. Chiron branched DNA
system
27. Direct Examination
Wave of the future:
DNA chip technology
detect viruses from
clinical specimens
tell viral load
determine antiviral agent
the virus is sensitive to
28. Indirect Examination
Virus amplification:
growing in tissue culture, eggs or
animals
Growing virus: changes
cytopathic effect (CPE)
ability to hemadsorb
Identity of virus confirmed by:
virus neutralization
Immunofluorescence
complement fixation
electron microscopy
29. Indirect Examination
Disadvantage of virus culture:
long time required for CPE
ability to hemadsorb to become
apparent
May take a few days to a few
weeks
Virus culture sensitivity: low and
depends on quality of clinical
specimen received
Not applicable to viruses that are
difficult or can not be cultivated
30. SEROLOGY
Remains the bulk of work carried
out by a routine diagnostic
laboratory
Complement fixation test
hemagglutination-inhibition
enzyme linked immunoassay
Radioimmunoassay
particle agglutination
Immunofluorescence
single radial hemolysis
western blot
31. SEROLOGY
Sensitivity and specificity rates vary
Most techniques will detect all
classes of antibody
Some assays like RIA, EIA and IF
can be made to detect one specific
class
IgM, IgG, IgA
Virus infections usually diagnosed
by serology:
* hepatitis A, B and C
32. DIFFICULT VIRUSES
Viral infections of the Central
nervous system
infection in immunocompetent
hosts
infection caused by HIV and
opportunistic infections
Viral pneumonias
Viral skin infections
Emerging viral infections
33. Viral infections of the CNS
Most cases of acute encephalitis in
immunocompetent hosts due to:
* HSV-1 and HSV-2
* EBV
* HHV-6 and HHV-7
Among immunocompromised
individuals:
* CMV
* VZV
34. Viral infections of the CNS
Diagnosis revolutionized
by availability of
cerebrospinal fluid (CSF)
polymerase chain reaction
analysis
PCR allows rapid, specific
and sensitive diagnosis
35. Viral infections of the CNS
CSF-PCR instead of brain biopsy
– Dx standard for HSV encephalitis
– mild or atypical cases
16-25% of cases
HSV
PCR analysis of CSF
–monitoring adequacy of therapy
–14day treatment with acyclovir
negative PCR
Prognosis:
– Determination of number of viral
DNA copies
36. Viral infections of the CNS
EBV semi-quantitative PCR
–significantly higher: active EBV
infection
– latently infected patients
seropositive: LOWER
positive EBV PCR in CSF
–sensitive and specific
primary CNS lymphoma in
patients with AIDS
CNS mass lesions
37. Viral infections of the CNS
HHV 6 and HHV 7
–Almost all children
–PCR
review of CSF specimens from
patients initially suspected to have
HSV encephalitis found HHV 6 DNA
in ~ 7% of specimens
– suggests HHV 6 may be an
important cause of sporadic focal
encephalitis
38. Viral infections of the CNS
Using CSF RT-PCR analysis
–most cases (85-95%) of acute
viral meningitis
enteroviruses
Signs and symptoms indicative of
encephalitis rather than
meningitis develop in ~ 3% of
patients
Patients with
agammaglobulinemia are at risk
for chronic enteroviral
meningoencephalitis
39. Viral Pneumonias
Causes in adults:
* Adenovirus * Influenza A & B
* CMV * Measles
* HSV * Parainfluenza
virus
* RSV * VZV
Causes in children
* Influenza A & B * Measles
* Parainfluenza * RSV
40. Diagnostic techniques for
herpesvirus infections
Virus Cytologic Viral Antigen Gene
evaluation culture detection ampli-
fication
HSV Cowdry CPE IFA PCR
Type A SVA ELISA
bodies
VZV Cowdry CPE IFA MRT-PCR
Type A
bodies
CMV “owl’s CPE IFA MRT-PCR
eye” cells SVA ELISA
41. Diagnostic techniques for
herpesvirus infections
Virus Cytologic Viral Antigen Gene
evaluation culture detection ampli-
fication
Highly CPE IFA MRT-PCR
RSV eosinophilic
intracytoplas SVA ELISA
mic
inclusions
Para Large cells HA IFA MRT-PCR
with single
influenza nucleus & SVA ELISA
multiple
small
eosinophilic
inclusions
Measles HA IFA
ELISA
42. Diagnostic techniques for
viral infections
Influenz HA IFA
a virus SVA ELISA
Adeno Intra- CPE IFA MRT-
virus nuclear SVA ELISA PCR
inclusions
43. Herpes virus skin infection
Diagnosis
Tzanck preparation :
–used to rapidly determine presence
of HSV or VZV
–does not distinguish between these
2 viruses
Stains : Giemsa,Wright’s, methylene
blue
Characteristic multinucleated giant
cells
– inexpensive, efficient provisional
diagnosis
44. Herpes virus skin infection
Diagnosis
HSV tissue culture: using
monoclonal antibodies, requires
only 24 hours
–sensitive test but expensive
Polymerase chain reaction
–expensive
Serology not very useful
– general population has antibodies to
herpes simplex
45. Emerging Viral Infections
Acute Hemorrhagic fever syndromes:
– Ebola and Marburg v
– Hantavirus
– Arena virus
Other viral encephalitis agents:
– Nipah virus (previously unknown
paramyxovirus)
46. Labtesting currently available
only at CDC:
–antigen detection
– IgM antibody detection
–isolation in cell culture
–visualization by electron
microscopy
– immunohistochemical
techniques
–RT-PCR
47. Emerging Viral Infections
Many of these “emerging” viral
infections are thought to pose a
serious risk as biologic weapons
Rapid diagnostics should be
made available worldwide in
order to detect as rapidly as
possible both justified and
unjustified suspects of HF and
attacks by other “biological
weapons”
48. Emerging Viral Infections
SARS
–Severe acute respiratory syndrome
–Killer pneumonia
Cause has yet to be identified
Laboratory tests found two types of
virus:
–paramyxovirus
–corona virus
A rapid diagnostic test should come
soon
50. SUMMARY
The non-specific nature of
clinical characteristics &
the extreme sensitivity of
lab techniques make the
diagnosis difficult, even
when a viral agent is
detected
51. SUMMARY
Understanding the
limitations of these
technological advances
and the use of
histopathological
techniques can greatly
enhance a skilled
clinician’s ability to make
an accurate diagnosis
56. ADENOVIRUS - Classification
• Subdivided into 6 subgroups based on
• hemagglutination (A-F)
• Human pathogens belong to 49 serotypes
• Common serotypes:- 1-8, 11, 21, 35, 37, 40
• Enteric Adenoviruses belong to subgroup F
57. ADENOVIRUS - Structure
Non-enveloped DNA virus
70-90 nm in size
Linear ds DNA genome with core proteins
59. ADENOVIRUS - Ultrastructure
Icosahedral capsid with 252 capsomeres
(12 pentons at vertices and 240 hexons)
Each penton has a fibers with terminal
knob projecting from it
65. Pathogenesis and Replication
• Infects mucoepithelial cells of
respiratory, GI and GU tracts
• Enter via epithelium, replicate
and spread to lymphoid tissue
• Viremia occurs
• Secondary involvement of
66. Pathogenesis and Replication
(contd.)
Fiber protein determines target cell
specificity and attachment
Viral DNA enters host cell nucleus
Virus replicates in cytoplasm
71. Types of infection
Lytic
Results in cell death; seen in mucoepithelical
cells
Latent/occult
Virus remains in host cell; seen in lymphoid
tissue, Groups B and C
Oncogenic Transformation
Uncontrolled cell growth and replication
occur; seen with Group A viruses in
hamsters
72. Adenovirus
Used as VECTORS to transfer desired
genetic material into cells e
Viral genome is relatively easily
manipulated in vitro
Efficient expression of inserted DNA in
recipient cell
73. Adenovirus- Properties
Stable in the environment
Relatively resistant to disinfection
(Alcohol, chlorhexidine, detergents)
Stable in GI tract- can withstand low
pH, bile acids and proteolytic enzymes
74. Time-course of infection
Incubation period- 2-14 days
Infective period continues for weeks
Intermittent and prolonged rectal
shedding
Secondary attack rate within families up
to 50%
75. Timecourse - Respiratory infection
Source- Medical Microbiology- Murray, Rosenthal, Kobayshi and Pfaller
76. EPIDEMIOLOGY
Endemic, epidemic and sporadic infections
Many infections are subclinical
77. EPIDEMIOLOGY-contd.
”Tip of the iceberg phenomenon”
Classical disease presentation
Mild clinical disease
Asymptomatic infection
but infectivity (+)
92. ADENOVIRAL INFECTIONS-
Genitourinary system
Acute hemorrhagic cystitis
fever, dysuria, hematuria
Types 11, 7, 4, 21, 1
More common in boys
Others
Orchitis, nephritis, cervicitis with
ulcerated vesicular lesions
Types 2, 19, 37
93. Other Infections due to
Adenovirus
•Myocarditis
•Pericarditis
•Meningitis
•Rash
•Arthritis
94. Adenovirus infections in
Immunocompromised hosts
Disseminated, severe and often fatal
infections
Due to new infection or reactivation of
latent virus
Prolonged infections with prolonged
viremia and viral shedding
Necrotizing pneumonia, hepatitis, rash,
DIC, CNS involvement
96. DIAGNOSIS
Variety of clinical specimens depending on
clinical syndrome-NP, conjunctival, stool,
urine,
tissue, etc.
Transport in viral transport media
Isolation from pharyngeal site correlates
better with current clinical infection
97. Methods for diagnosis
Culture in HeLa, HEK cell lines
Shell vial cell culture
DFA
PCR, nucleic acid probes
EM and Immune EM
98. Diagnosis-
Enteric adenoviruses
Isolation
requires special media-
Graham 293
ELISA for rapid detection is
available
99. Prevention
Good handwashing
Contact precautions
Chlorination of water
Disinfection or
sterilization of
ophthalmologic
equipment
Use of single dose vials
Oral vaccine- restricted
100. HIV and AIDS
The cellular and immunological picture - The course of
the disease
101. HIV and AIDS
The cellular and immunological picture - The course
of the disease
102. HIV and AIDS
The cellular and immunological picture
The course of the disease
1. Acute Infection
• High virus titer
• Mild symptoms
• Fall in CD4+ cells but recovers
• Rise in CD8+ cells but recovers
• A high virus titer (up to 10 million
Macrophages bring HIV into the body if se
viruses per ml blood)
103. HIV and AIDS
2. A strong immune response
Virus almost disappears from circulation
• Good cytoxic T cell response
• Soluble antibodies appear later against both
surface and internal proteins
• Most virus at this stage comes from recently
activated (dividing) and infected CD4+ cells
104. HIV and AIDS
3. A latent state
Latency of virus and of symptoms
• Virus persists in extra-vascular
tissues
• Lymph node dendritic cells
• Resting CD4+ memory cells (last a
very
long time - a very stable population of
cells) carry provirus
105. HIV and AIDS
• 10 billion HIV particles per day
• Virus half life 5.7 hours
• 100-10 million virions per ml blood (set point)
• Small minority of T4 cells are infected
• Virus found in lymph nodes
106. HIV and AIDS
4. The beginning of disease
Massive loss of CD4+ cells
• CD4+ cells are the targets of the virus
• Cells that proliferate to respond to the
virus are killed by it
• Dendritic cells present antigen and virus
to CD4 cells
• Epitope variation allows more and more
HIV to
escape from immune response just as
107. HIV and AIDS
5. Advanced disease - AIDS
CD8+ cells destroy more
CD4+ cells
• CD4 cell loss means virus and
infected
cells no longer controlled
• As CD4+ cells fall below 200
per cu mm
virus titer rises rapidly and
remaining immune response
108. HIV and AIDS
Good correlation betw
number of HIV particle
measured by PCR an
progression to disease
110. HIV and AIDS
CD4 cell count is not
good predictor of
progression to diseas
111. HIV and AIDS
Cofactors
Not all cases of Kaposi’s are associated with HIV
Not all HIV infected persons suffer from Kaposi’s
20% of homosexual HIV+ males get Kaposi’s
Few IV drug users or hemophiliacs get Kaposi’s
Kaposi’s sarcoma associated herpes virus
Human herpes virus-8
112. HIV and AIDS
Three Views of AIDS
Gallo: Infection by HIV is sufficient to cause AIDS
Montagnier: HIV may be harmless in the absence of other co-
factors
Duesberg / Mullis: HIV is too silent to be the etiologic agent of
AIDS. It is a much maligned by-stander
So far it seems that >50% of HIV-infected persons have
progressed to AIDS
There is NO strong evidence there is any other infectious
agent involved than HIV
113. HIV - The Virus
Retrovirus
Membrane: host derived
Three genes
GAG – POL – ENV
114. HIV - The Virus
Retrovirus
Two glycoproteins: gp160 gp120 and gp41
gp41 is fusogen that spans the membrane
sugars vaccine problem
ENV gene
115. HIV - The Virus
Retrovirus
Group-Specific Antigens
p17: inner surface - myristoylated
p24: nucleocapsid
p9: nucleocapsid associated with RNA
GAG gene
Polyprotein
116. HIV - The Virus
Enzymes Retrovirus
• Polymerase (reverse
transcriptase – RNA
dependent DNA
polymerase)
• Integrase
• POL gene
• Protease (cuts
Polyprotein
polyproteins)
117. The Genome of HIV
Three structural genes
LTRs
Extra open reading frames are clue to latency
119. HIV - The Virus
Life History
A retrovirus
• Latency
• Specific destruction of
CD4+ cells
120. HIV - Life History
• Fusion at ambient pH
• No need for entry
into lysosomes
•Profound significance
Syncytia
for AIDS progression:
Spread from cell to
cell
Profound significance
121. HIV - Life History
Entry into the cell
T4 (CD4+) cells are major
target
Human HeLa
Human
Cell transfected
HeLa Cell
with CD4 antigen
NOT INFECTED INFECTED
But NOT the whole answer since this
does not happen if CD4 is transfected in
122. HIV - Life History
Why do CD4-transfected human cell
but CD4-transfected mouse cells do
Human cells must possess a co-factor for infection that mou
Co-Receptors
CD8+ Cells
MIP-1 alpha MIP-1 beta RANTES
Chemokines
123. HIV - Life History
HIV
chemoki
Mutant
CD4 ne
CCR5 CCR5
CCR5 CD4
CD4
macrophage
Chemokine receptors are necessary co-recep
124. HIV and AIDS
Some people do not get AIDS
Long term survivors
Exposed uninfected persons
The chemokine receptor story
125. HIV and AIDS
Co-receptors and HIV infection
• CCR5 is a chemokine receptor
• Cells with homozygous mutant CCR5 molecules are not
infected by HIV
1 in 100 Caucasians
No Africans
• Persons with heterozygous mutant CCR5 molecules
progress to AIDS more slowly
126. HIV and AIDS
Co-receptors
• 25% of long term survivors are CCR5 or CCR2
mutants (deletions)
• The same CCR5 mutation (called “delta 32”) is
thought to be the mutation that rendered some
people immune to the plague in the middle
ages
• Many other chemokine receptors
127. HIV and AIDS
Long term non-progressers
People who have been infected with
HIV for more than seven years that
have stable CD4+ cell counts above
600 per cu mm with no symptoms and
no chemotherapy
Many have produced a very good
immune response to the virus
128. HIV and AIDS
• Nairobi prostitutes
Client infection rate more than 25%
• Rare HLA antigens
• Associations between resistance to infection and their
class I and class II MHC (HLA) haplotypes
129. HIV - Life History
HIV is a retrovirus
It carries with it:
• Reverse transcriptase HIV genes
• Integrase GAG POL
• Protease ENV
• tRNA primer
HIV has no oncogene but could still be oncogenic
vaccine problem
130. HIV - Life History
Latency – Cellular – The problem of memory T4 cells
Only activated T4 cells can replicate virus
Most infected T4 cells are rapidly lyzed but are replaced
Some T4 cells revert to resting state as memory cells wh
Memory T4 cells cannot replicate the virus unless they b
Clinical Latency
HIV infection is not manifested as disease for years
131. Dynamics of CD4 T cells in an
HIV infection
Cell death Chronically-
apoptosis etc infected
memory T
Return to cells with
Infection resting
Uninfected state provirus
activat
ed Long
T cell Reactivation
lived!
Uninfected Cell death Long
unactivated
memory
immune lived!
Adapted from Saag and Kilby
T cell pool destruction Nat Med 5: 609, 1999
132. Long tern latent HIV
Immune response
T4 resting T4 activated
It may be impossible to cure the patient o
Even if combination therapy stops HIV re
HIV
133. Inexorable decline of CD4+
T4 cells
Why do all
of the T4
cells
At early
disappear?
stages of
infection
only 1 in
10,000 cells
is infected
Of great importance to therapeutic strategy
134. Virus destroys the cell as a result of
budding
But few cells are infected:
Early stage of infection 1:10,000
Late 1:40
Why do all T4
cells
1. PUNCTURED disappear?
MEMBRANE
135. Why do all T4 cells
disappear? - 2
But syncytia
not common
Infected CD4
Cells
cell Most T4 cells
Fuse
Gp120 are not HIV+
positive
Could
“sweep up”
Uninfected
Killing of CD4 cells CD4 cell uninfected
2. Syncytium Gp120 cells
Formation negative
136. Why do all T4
cells
disappear?
Cytotox
ic T cell
Killing of CD4 cells
3. Cytotoxic T cell-
BUT: Most mediated lysis
cells are
137. Killing of
CD4+ cells
4. Binding of free
Gp120 to CD4
antigen makes
uninfected T4 cell
look like an
infected cell
Complement-
mediated lysis
138. Why do all T4 cells
disappear?
Induction of apoptosis
CD8 gp120
Macrophag
HIVcell e
(no CD4 antigen)
chemokin
e
CXCR
4 G protein
signal
?
?
Binding to
Binding to
CXCR4
CXCR4 results results in
in expression expression of
of TNF-alpha TNF-alpha on
139. Why do all T4 cells
disappear?
Induction of apoptosis
CD8 cell
CXCR
4 Macrophag
Deat e
h
CD8 T
cell
140. Macrophages may be infected
by two routes
HIV gp120
CD4
HIV gp120 binds to
macrophage CD4
antigen
Virus is opsonized
by anti gp120
antibodies which
Fc receptor bind to macrophage
Fc receptors - an
Anti-gp120 vaccine problem
enhancing antibody
HIV
142. Viral Hepatitis - Overview
Types of Hepatitis
A B C D E
Source of Feces Blood Blood Blood Feces
Blood-derived Blood-derived Blood-derived
Virus body fluids body fluids body fluids
Route of Fecal-Oral Percutaneous Percutaneous Percutaneous Fecal-
Trans- Permucosal Permucosal Permucosal Oral
mission
Chronic No Yes Yes Yes No
Infection
Primary Pre/Post- Pre/Post- Blood Donor Pre/Post- Ensure safe
Exposure Exposure Screening Exposure drinking
Prevent- Immunization water
Immunization Immunization
ion Risk Behavior
Handwashing Risk Behavior Modification Risk Behavior
Modification Modification
143. Hepatitis A, B, and C at a Glance
Virus Sex IDU Trans- Fecal- Occu- Course of Infection Does Vaccine
fusion Oral pational Protective Available
Immunity
Develop?
A High Low* Low High None Acute -> Resolved Yes Yes
B High High Low None High Acute -> Chronic Yes Yes
90% of infants
30% in children aged 1-5
10% of older children and
adults.
C Low High Low None Low Acute -> Chronic No No
in 75%-85% of adults.
148. Hepatitis A Virus: Structure and
Classification
RNA Picornavirus
• Separate genus because of differences
with other enteroviruses
• Naked icosahedral capsid
• SS RNA (740 nucleotides)
• Single serotype worldwide
• Humans only reservoir
149. HEPATITIS A VIRUS TRANSMISSION
• Fecal-oral transmission
• Close personal contact
(e.g., household contact, sex
contact, child day-care centers)
• Contaminated food, water
(e.g., infected food handlers,
contaminated raw oysters)
• Blood exposure (rare <<<1%)
(e.g., injection drug use, rarely
by transfusion)
150. HEPATITIS A, UNITED STATES
Most disease occurs in the context of community-
wide outbreaks
Infection transmitted from person to person in
households and extended family settings
- facilitated by asymptomatic infection among
children
Some groups at increased risk
– specific factor varies
– do not account for majority of cases
– Children are the most frequently infected group
No risk factor identified for 40%-50% of cases
151. DISEASE BURDEN FROM
HEPATITIS A
UNITED STATES, 2001
Number of acute clinical 10,609
cases reported
Estimated number of acute 45,000
clinical cases
Estimated number of 93,000
new infections
Percent ever infected 31.3%
153. NUMBER OF YEARS REPORTED INCIDENCE OF
HEPATITIS A EXCEEDED 10 CASES PER 100,000,
BY COUNTY, 1987-1997
0-1 2-3 4-5 6-7 8-11
154. Hepatitis A: Pathogenesis
Incubation 4 weeks (range 2-6 weeks)
Oral cavityGI tractliver via blood
Replicates in hepatocytes (little damage
to cells) released via bile to intestines
7-10 days prior to clinical symptoms
Liver damage and clinical syndrome
result of immune response and not
direct effect of virus
155. Hepatitis A: Clinical Features
– An acute illness with:
discrete onset of symptoms (e.g.
fatigue, abdominal pain, loss of
appetite, intermittent nausea, vomiting)
jaundiceor elevated serum
aminotransferase levels, dark urine, light
stool
Adults usually more symptomatic
Patients are infective while they are
shedding the virus in the stool- usually
before the onset of symptoms
Mostcases resolve spontaneously in 2-4
weeks
Complete recovery 99%
156. HEPATITIS A - CLINICAL FEATURES
•Jaundice by <6 yrs <10%
age group: 6-14 yrs
40%-50%
>14 yrs
70%-80%
•Rare complications: Fulminant hepatitis
Cholestatic
hepatitis
Relapsing
hepatitis
•Incubation period: Average 30 days
Range 15-50 days
157. EVENTS IN HEPATITIS A VIRUS INFECTION
Clinical illness
Infection ALT
IgM IgG
Response
Viremia
HAV in stool
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Week
158. Hepatitis A Diagnosis
Detection of IgM antibody
IgG positive 1-3 weeks later;
suggests prior infection or
vaccination.
159. Hepatitis A Treatment
Supportive- no specific role of
antiviral therapy
Lifelong immunity likely after
infection or vaccination
160. PREVENTING HEPATITIS A
• Hygiene (e.g., hand washing)
• Sanitation (e.g., clean water
sources)
• Hepatitis A vaccine (pre-exposure)
• Immune globulin (pre- and post-
exposure)
161. HEPATITIS A VACCINES
• Inactivated vaccine
• Highly immunogenic
•97%-100% of children, adolescents, and
adults have protective levels of antibody
within 1 month of receiving first dose;
essentially 100% have protective levels
after second dose
• Highly efficacious
•In published studies, 94%-100% of
children protected against clinical hepatitis
A after equivalent of one dose
163. POST-VACCINATION TESTING
Not recommended:
High response rate among vaccinees
Commercially available assay not
sensitive enough to detect lower
(protective) levels of vaccine-induced
antibody
164. DURATION OF PROTECTION AFTER
HEPATITIS A VACCINATION
Protection begins 4 weeks after vaccine
Persistence of antibody
• At least 5-8 years among adults and
children
Efficacy
– No cases in vaccinated children at 5-6 years
of follow-up
Mathematical models of antibody
decline suggest protective antibody
levels persist for at least 20 years
Other mechanisms, such as cellular
memory, may contribute
165. Hepatitis A Vaccine
Recommendations
Vaccine is recommended for the following
persons 2 years of age and older:
– Travelers to areas with increased rates of hepatitis A
– Men who have sex with men
– Injecting and non-injecting drug users
– Persons with clotting-factor disorders (e.g.
hemophilia)
– Persons with chronic liver disease
– Children living in areas with increased rates of
hepatitis A during the baseline period from 1987-
1997- mainly West Coast.
166. Hep A : Passive Immunization
Hepatitis A immune globulin can be
given up to 2 weeks after an
exposure
Immunity temporary (4-5 months)
Also given in travelers leaving for
endemic area on short notice (ie not
enough time for the vaccine to be
effective)
167. Hepatitis A Surveillance & Response
Urgently reportable condition in S.C. –
Acute HAV infection must be reported
by phone to DHEC within 24 hours.
Investigation of a case of hepatitis A
must be initiated by CO DADE and
district epi staff within 24 hours of
notification.
All cases must be reported to CDC.
170. Hepatitis B: Structure
Member of the hepadnavirus group
Virion also referred to as Dane particle
42nm enveloped virus
Core antigens located in the center
(nucleocapsid)
– Core antigen (HbcAg)
– e antigen (HBeAg)- an indicator of
transmissibility (minor component of the
core- antigenically distinct from HBcAg)
22nm spheres and filaments other
forms- no DNA in these forms so they
are not infectious (composed of surface
antigen)- these forms outnumber the
actual virions
171. Structure and Replication
Circular partially double stranded DNA of virus
Initial replication to complete circular DNA
with subsequent transcription to make several
mRNAs some of which are translated into viral
proteins
One of the mRNAs is replicated with a reverse
transcriptase making the DNA that will
eventually be the core of the progeny virion
Some DNA integrates into host genome
causing carrier state
Virus stable and resist many stresses making
them more infectious
173. Epidemiology - United States1
100,000 new infections per year
8,000 - 32,000 chronic
infections/year
5,000 - 6,000 deaths/year
1.25 million Americans with chronic
HBV infection
– 15 to 25% of chronically infected
patients will die from chronic liver
disease
1. Center for Disease Control
174. Geographic Distribution of Chronic HBV Infection
HBsAg Prevalence
8% - High
2-7% - Intermediate
<2% - Low
175. High Prevalence of CHBV in Asian
American Communities is Often Overlooked1
US prevalence for chronic HBV is < 2%
However, chronic HBV prevalence of 10-
15% in Asian American communities has
been reported
In Asian American men living in
California, HCC ranks as a leading cause
death
– #2 in Vietnamese and Cambodian Americans
– #4 in Chinese and Korean Americans
50% of children born to mothers with
chronic HBV in the US are Asian American
1. www.liver.stanford.edu
177. Concentration of Hepatitis B Virus
in Various Body Fluids
Low/Not
High Moderate Detectable
blood semen urine
serum vaginal fluid feces
wound exudates saliva sweat
tears
breastmilk
178. Risk Factors for Acute Hepatitis B
United States, 1992-1993
Heterosexual*
(41%)
Injecting
Drug
Use Homosexual Activity
(15%) (9%)
Household Contact
(2%)
Health Care Employment
(1%)
Unknown (31%)
Other (1%)
* Includes sexual contact with acute cases, carriers, and multiple partners.
Source: CDC Sentinel Counties Study of Viral Hepatitis
179. HBV Pathogenesis
Virus enters hepatocytes via blood
Immune response (cytotoxic T cell) to
viral antigens expressed on hepatocyte
cell surface responsible for clinical
syndrome
5 % become chronic carriers (HBsAg> 6
months)
Higher rate of hepatocellular ca in
chronic carriers, especially those who
are “e” antigen positive
Hepatitis B surface antibody likely
confers lifelong immunity
Hepatitis B e Ab indicates low
180. Hepatitis B - Clinical Features
• Incubation period: Average 60-90 days
Range 45-180 days
• Clinical illness (jaundice): <5 yrs, <10%
5 yrs, 30%-50%
1/3 adults-no
symptoms
• Acute case-fatality rate: 0.5%-1%
• Chronic infection: <5 yrs, 30%-90%
5 yrs, 2%-10%
• More likely in asymptomatic infections
• Premature mortality from
chronic liver disease: 15%-25%
181. Hepatitis B Clinical Features
Incubation Period: 6 weeks to 6 months (av.
120 days)
Preicteric or Prodromal phase from initial
symptoms to onset of jaundice usually lasts
from 3 to 10 days: Non-specific, insidious
onset of malaise, anorexia, n/v, RUQ
pain, fever, headache, myalgias, skin
rashes, arthralgias, arthritis, and dark urine
beginning 1-2 days before onset of jaundice.
182. Hepatitis B Clinical Features
Icteric phase usually lasts from 1-3 weeks:
jaundice, light or gray stools, hepatic
tenderness, hepatomegaly.
Convalescence phase may persist for weeks or
months: Malaise, fatigue.
Jaundice, anorexia, and other symptoms
disappear.
183. Hepatitis B Symptoms
About 50%-60% of adults with HBV infection have no
signs or symptoms.
Those who do have symptoms might experience:
Jaundice
Fatigue
Abdominal pain
Loss of appetite
Nausea, vomiting
Joint pain
184. Outcome of Hepatitis B Virus Infection
100 by Age at Infection 100
Symptomatic Infection (%)
80 80
Chronic Infection
60 60
Chronic Infection
40 40
(%)
20 20
Symptomatic Infection
0 0
Birth 1-6 months 7-12 months 1-4 years Older Children
and Adults
Age at Infection
185. Possible Outcomes of HBV Infection
Acute
hepatitis B
95% of infection 3-5% of
infant-
Chronic HBV adult-
acquiredinfection acquired
infectionsChronic infections
12-25% in
hepatitis
6-15% in 5 Cirrhosi years
5 20-23% in
years
Hepatocell s 5 years
Liver
ular failure
Death
carcinoma Liver Death
186. Acute Hepatitis B Virus Infection with Recovery
Typical Serologic Course
Symptoms
HBeAg anti-HBe
Total anti-HBc
Titer
HBsAg IgM anti-HBc anti-HBs
0 4 8 12 16 20 24 28 32 36 52 100
Weeks after Exposure
187. Progression to Chronic Hepatitis B Virus Infection
Typical Serologic Course
Acute Chronic
(6 months) (Years)
HBeAg anti-HBe
HBsAg
Total anti-
HBc
Titer
IgM anti-
HBc
0 4 8 1 1 2 2 2 3 3 5 Years
Weeks 6 0 4 8 2 6
2 after Exposure 2
188.
189. INTERPRETATION OF THE HEPATITIS B PANEL
Tests Results Interpretation
HBsAg Negative Susceptible
Anti-HBc Negative
Anti-HBs Negative
HBsAg Negative Immune
Anti-HBc Negative or Positive
Anti-HBs Positive
HBsAg Positive
Anti-HBc Positive Acute Infection
IgM Anti-HBc Positive
Anti-HBs Negative
HBsAg Positive Chronic Infection
Anti-HBc Positive
IgM Anti-HBc Negative
Anti-HBs Negative
HBsAg Negative Four possible interpretations
Anti-HBc Positive
Anti-HBs Negative
190. Interpretation
HBsAg negative
HBcAb positive
HBsAb negative
1. May be recovering from acute infection.
2. May be distantly immune and test is not
sensitive enough to detect very low level of
HBsAb in serum.
3. May be susceptible with a false positive
HBcAb.
4. May be undetectable level of HBsAg present
in the serum and the person is actually a
carrier.
191. Current Treatment Options for HBV
Pegylated Interferon alfa (Intron A)
Lamivudine (Epivir HBV)
Adefovir dipivoxil (Hepsera)
192. Elimination of Hepatitis B Virus
Transmission United States
Strategy
• Prevent perinatal HBV transmission
• Routine vaccination of all infants
• Vaccination of children in high-risk groups
• Vaccination of adolescents
– all unvaccinated children at 11-12 years of
age
– “high-risk” adolescents at all ages
193. Hepatitis B Vaccine
Infants: several options that depend on
status of the mother
– If mother HepBsAg negative: birth, 1-2m,6-
18m
– If mother HepBsAg positive: vaccine and
Hep B immune globulin within 12 hours of
birth, 1-2m, <6m
Adults
– 0, 1, 6 months
Vaccine recommended in
– All those aged 0-18
– Those at high risk
194. Hepatitis B High Risk Groups
Persons with multiple sex partners or diagnosis of a
sexually transmitted disease
Men who have sex with men
Sex contacts of infected persons
Injection drug users
Household contacts of chronically infected persons
Infants born to infected mothers
Infants/children of immigrants from areas with high
rates of HBV infection
Health care and public safety workers
Hemodialysis patients
195. Estimated Incidence of Acute Hepatitis B
United States, 1978-1995
80 HBsAg
screening Infant
Vaccine of pregnant immunization
70 licensed women recommende
recommended d
60
OSHA Rule
50 enacted
Population
Cases per
Adolescent
100,000
40 immunization
recommende
d
30
20
*
Decline
among Decline
10 among
homosexual
men & injecting
0 HCWs drug users
78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
* Provisional date Year
196. Hepatitis B: Passive Immunization
Infants of surface antigen positive
mothers
Exposures to infected blood or
infected body fluids in individuals
who are unvaccinated, unknown
vaccination, or known non-
responders.
– Ideally within 24 hours
– Probably not effective >7days post
exposure
197. Hepatitis B Surveillance
Acute Hepatitis B is an urgently
reportable condition. It must be
reported by phone to DHEC within 24
hours.
Chronic Hepatitis B is a reportable
condition and must be reported to
DHEC within 7 days.
Perinatal Hepatitis B is a reportable
condition and must be reported to
198. Hepatitis B Surveillance
Acute,chronic, and perinatal
hepatitis B must be reported to CDC.
CDC and S.C. conducts enhanced
surveillance on acute and perinatal
hepatitis B cases.
200. Hepatitis D Structure
Defective virus that requires co-
infection with hepatitis B for
replication
Enveloped with SS RNA genome
Onlyantigen encoded in the delta
antigen
202. Hepatitis D Virus
Modes of Transmission
• Percutaneous exposures
– injecting drug use
• Permucosal exposures
– sex contact
203. Geographic Distribution of HDV Infection
Taiwan
Pacific Islands
HDV Prevalence
High
Intermediat
e
Low
Very Low
No Data
204. Hepatitis D:Pathogenesis
Pathogenesis
– Immune mediated
– Co-infection- infection with B at the
same time (more severe)
– Superinfection: acquisition of Hep D in
chronically Hep B
210. Hepatitis D - Prevention
• HBV-HDV Coinfection
Pre or postexposure prophylaxis to prevent HBV
infection
• HBV-HDV Superinfection
Education to reduce risk behaviors among persons with
chronic HBV infection
• Alpha interferon may help reduce hepatocellular
damage
212. Hepatitis C Structure and
Classification
Member of the flavivirus family
(other members yellow fever and
dengue)
Enveloped single stranded RNA virus
Humans and chimpanzees only
known reservoirs
6 serotypes (genotypes) and multiple
subtypes based on high variability of
envelope glycoproteins
213. Hepatitis C Virus Infection, United States
New infections per year 1985-89 242,000
2001 25,000
Deaths from acute liver failure Rare
Persons ever infected (1.8%) 3.9 million
(3.1-4.8)*
Persons with chronic infection 2.7 million
(2.4-3.0)*
HCV-related chronic liver disease 40% - 60%
Deaths from chronic disease/year 8,000-10,000
*95% Confidence Interval
214. Estimated Incidence of Acute HCV
Infection
United States, 1960-2001
140
New Infections/100,000
120
100 Decline in injection
80 drug users
60
40 Decline in
transfusion recipients
20
0
1960 1965 1970 1975 1980 1985 1989 1992 1995 1998 2001
Year
Source: Hepatology 2000;31:777-82; Hepatology 1997;26:62S-65S;
CDC, unpublished data
215. Exposures Known to Be Associated With
HCV Infection in the United States
Injecting drug use
Transfusion, transplant from infected
donor
Occupational exposure to blood
– Mostly needle sticks
Iatrogenic (unsafe injections)
Birth to HCV-infected mother
Sex with infected partner
– Multiple sex partners
216. Sources of Infection for
Persons With Hepatitis C
Injecting drug use 60% Sexual 15%
Transfusion 10%
(before screening)
Occupational 4%
Other 1%*
Unknown 10%
* Nosocomial; iatrogenic; perinatal
Source: Centers for Disease Control and Prevention
217. Posttransfusion Hepatitis C
30 All volunteer donors
HBsAg
% of Recipients Infected
25
20
15 Donor Screening for HIV Risk Factors
Anti-HIV
10 ALT/Anti-HBc
Anti-HCV
5 Improved
HCV Tests
0
1965 1970 1975 1980 1985 1990 1995 2000
Year
Adapted from HJ Alter and Tobler and Busch, Clin Chem 1997
218. Injecting Drug Use and HCV
Transmission
Highly efficient
– Contamination of drug
paraphernalia, not just needles and
syringes
Rapidly acquired after initiation
– 30% prevalence after 3 years
– >50% after 5 years
Four times more common than HIV
219. Occupational Transmission of
HCV
Inefficient by occupational exposures
Average incidence 1.8% following
needle stick from HCV-positive source
– Associated with hollow-bore needles
Case reports of transmission from blood
splash to eye; one from exposure to
non-intact skin
Prevalence 1-2% among health care
workers
– Lower than adults in the general population
– 10 times lower than for HBV infection
220. Perinatal Transmission of HCV
Transmission only from women HCV-
RNA positive at delivery
– Average rate of infection 6%
– Higher (17%) if woman co-infected with
HIV
– Role of viral titer unclear
No association with
– Delivery method
– Breastfeeding
Infected infants do well
– Severe hepatitis is rare
221. Sexual Transmission of HCV
Occurs, but efficiency is low
– Rare between long-term steady partners
– Factors that facilitate transmission between
partners unknown (e.g., viral titer)
Accounts for 15-20% of acute and
chronic infections in the United States
Partner studies
– Low prevalence (1.5%) among long-term
partners
infections
might be due to common percutaneous
exposures (e.g., drug use), BUT
– Male to female transmission more efficient
more indicative of sexual transmission
222. Household Transmission of HCV
Rare but not absent
Could occur through
percutaneous/mucosal exposures
to blood
– Contaminated equipment used for
home therapies
IV therapy, injections
– Theoretically through sharing of
contaminated personal articles
(razors, toothbrushes)
223. Other Potential Exposures to Blood
No or insufficient data showing
increased risk
– intranasal cocaine use, tattooing, body
piercing, acupuncture, military service
No associations in acute case-control or
population-based studies
Cross-sectional studies in highly
selected groups with inconsistent results
– Temporal relationship between exposure
and infection usually unknown
– Biologically plausible, but association or
causal relationship not established
224. Hep C: Pathogenesis
Blood-borne pathogen that infects
hepatocytes
Much like Hep A and B, liver damage
and clinical illness due more to elicited
immune response as opposed to direct
cytopathic effect of the virus
Likely cytotoxic T cells that mediate
most of the damage
Like other chronic liver diseases (Hep B
and chronic alcoholism), can cause
hepatocellular ca (HCC)
Some genotypes more amenable to
therapy- i.e. 3a
225. Features of Hepatitis C Virus Infection
Incubation period Average 6-7 weeks
Range 2-26 weeks
Acute illness (jaundice) Mild (<20%)
Case fatality rate Low
Chronic infection 60%-85%
Chronic hepatitis 10%-70% (most
asx) Age-
Cirrhosis related <5%-20%
Mortality from CLD 1%-5%
226. Hepatitis C: Clinical Features
Acuteinfection asymptomatic in over
80% of patients, when present,
acute illness usually mild
– Acute symptoms include jaundice,
nausea, abdominal pain, loss of
appetite, dark urine
227.
228. Hepatitis C: Extrahepatic Manifestations
Seen with chronic infection
? Due to immune complexes
Extrahepatic manifestations
– Essential mixed cryoglobulinemia
(vasculitis, skin rash, fatigue)
– Porphyria cutanea tarda
– Membranoproliferative glomerulonephritis
– ?Diabetes mellitus
– Other autoimmune disease
– ?Lymphoma
230. Chronic Hepatitis C
Factors Promoting Progression or
Severity
Increased alcohol intake
Age > 40 years at time of infection
HIV co-infection
Other
– Male gender
– Chronic HBV co-infection
231. Serologic Pattern of Acute HCV Infection
with Recovery
anti-
Symptoms +/- HCV
HCV RNA
Titer
ALT
Norm
0 1 2 3 al 5 6 1 2 3 4
4
Mont Year
Time after Exposure
hs s
232. Serologic Pattern of Acute HCV Infection with
Progression to Chronic Infection
anti-
Symptoms +/- HCV
HCV RNA
Titer
ALT
Norm
0 1 2 3 4 al 6 1 2 3 4
5
Mont Year
Time after Exposure
hs s
233. Hepatitis C: Diagnosis
ELISA-a serological test which is usually.
positive within 2-5 months after infection
– 3rd generation assays now 99% specific and
sensitive
Confirmatory testing
– PCR (positive 1-2 weeks post infection) both
quantitative and qualitative (I.e. ye/no)
available
– RIBA (recombinant immunoblot assay)- looks
for 2 or more antibodies to HCV viral antigens
Genotype testing done when treatment
anticipated
234. HCV Testing Routinely Recommended
Based on increased risk for infection
Ever injected illegal drugs
Received clotting factors made before
1987
Received blood/organs before July 1992
Ever on chronic hemodialysis
Evidence of for exposure management
Based on need liver disease
Healthcare, emergency, public safety
workers after needle stick/mucosal
exposures to HCV-positive blood
Children born to HCV-positive women
235. HCV Infection Testing Algorithm
for Diagnosis of Asymptomatic Persons
Screening Test for Negative
STOP
Anti-HCV
Positive
OR
RIBA for Negative NAT for HCV
Anti-HCV RNA
Negative Indeterminate Positive Positive
Additional Laboratory Medical
STOP Evaluation (e.g. PCR, ALT) Evaluation
Negative PCR, Positive PCR,
Normal ALT Abnormal ALT
Source: MMWR 1998;47 (No. RR 19)
236. Medical Evaluation and Management
for Chronic HCV Infection
Assess for biochemical evidence of CLD
Assess for severity of disease and
possible treatment, according to current
practice guidelines
– 40-50% sustained response to antiviral
combination therapy (peg
interferon, ribavirin)
– Vaccinate against hepatitis A
Counsel to reduce further harm to liver
– Limit or abstain from alcohol
237. Hepatitis C Therapy
Standard of care is pegylated
interferon alpha and ribavirin
Many barriers to treatment as the
above regimen is difficult to take
and has many systemic side
effects
(fatigue, myalgias, depression, ane
mia to name a few)
Overall response rate to treatment
238. Postexposure Management for HCV
IG, antivirals not recommended for
prophylaxis
Follow-up after needlesticks, sharps, or
mucosal exposures to HCV-positive blood
– Test source for anti-HCV
– Test worker if source anti-HCV positive
Anti-HCV and ALT at baseline and 4-6 months later
For earlier diagnosis, HCV RNA at 4-6 weeks
– Confirm all anti-HCV results with RIBA
Refer infected worker to specialist for
medical evaluation and management
240. Hepatitis E
Non-enveloped single stranded RNA
virus
Resembles calicivirus or Norwalk
agent
Similarillness to Hep A except high
mortality in pregnant women
241. Geographic Distribution of Hepatitis E
Outbreaks or Confirmed Infection in >25% of Sporadic Non-ABC
Hepatitis
242. Hepatitis E -
Epidemiologic Features
• Most outbreaks associated with
fecally contaminated drinking water
• Minimal person-to-person
transmission
• U.S. cases usually have history of
travel
to HEV-endemic areas
243. Hepatitis E - Clinical Features
• Incubation period: Average 40 days
Range 15-60 days
• Case-fatality rate: Overall, 1%-3%
Pregnant women,
15%-25%
• Illness severity: Increased with age
• Chronic sequelae: None identified
244. Hepatitis E Virus Infection
Typical Serologic Course
Symptoms
ALT
IgG anti-
HEV
IgM anti-
Titer
HEV
Virus in
stool
0 1 2 3 4 5 6 7 8 9 1 1 1 1
Weeks after Exposure 0 1 2 3
245. Prevention and Control Measures
for Travelers to HEV-Endemic
Regions
• Avoid drinking water (and beverages with ice) of
unknown purity, uncooked shellfish, and uncooked
fruit/vegetables not peeled or prepared by traveler
• IG prepared from donors in Western countries
does not prevent infection
• Unknown efficacy of IG prepared from donors in
endemic areas
• Vaccine?
249. „FLU‟
True influenza
– influenza virus A or influenza virus B (or
influenza virus C infections - much
milder)
Febrilerespiratory disease with
systemic symptoms caused by a
variety of other organisms often
inaccurately called „flu‟
250. South Carolina 1996-1997 DHEC bulletin
malathia influenzae per le stel
no virus
CULTURE
RESULTS
influenza A
influenza B
http://www.state.sc.us/dhec/LAB/labbu017.htm
251. THE IMPACT OF INFLUENZA
PANDEMICS
Deaths:
1918-19 Spanish flu 500,000 US
20,000,000 world
1957-58 Asian flu 70,000 US
252. THE IMPACT OF INFLUENZA
In the United States, on average:
36,000 deaths per year
114,000 hospitalizations per year
CDC: MMWR 53:8-11, 2004
253. THE IMPACT OF INFLUENZA
recently
some increase in morbidity
and mortality - possible factors?
– more elderly people
– CF patients live longer
– more high risk neonates
– more immunosuppressed patients
255. ORTHOMYXOVIRUSES
HA - hemagglutinin
NA - neuraminidase
helical nucleocapsid (RNA plu
NP protein)
lipid bilayer membrane
polymerase complex
M1 protein
type A, B, C : NP, M1 protein
sub-types: HA or NA protein
256. TRANSMISSION
AEROSOL
– 100,000 TO
1,000,000
VIRIONS PER
DROPLET
18-72 HR
INCUBATION
SHEDDING
257. NORMAL TRACHEAL MUCOSA
3 DAYS POST-INFECTION 7 DAYS POST-INFECTION
Lycke and Norrby Textbook of Medical Virology 1983
258. DECREASED
CLEARANCE
RISK BACTERIAL
INFECTION
VIREMIA RARE
Lycke and Norrby Textbook of Medical Virology 1983
259. RECOVERY
INTERFERON - SIDE EFFECTS
INCLUDE:
– FEVER, MYALGIA, FATIGUE, MALAISE
CELL-MEDIATED IMMUNE RESPONSE
TISSUE REPAIR
– CAN TAKE SOME TIME
263. INTERFERON
antiviral state
antiviral state antiviral state
antiviral state
264. INTERFERON
antiviral state
antiviral state antiviral state
antiviral state
265. INTERFERON
antiviral state
antiviral state antiviral state
antiviral state
266. INTERFERON
THE VIRUSES ARE COMIN
PAUL REVERE
http://www.mfa.org/collections/one_hour/6.htm
http://www.paulreverehouse.org/midnight.html
267. TYPES OF INTERFERON
TYPE I
Interferon-alpha (leukocyte
interferon, about 20 related
proteins)
- leukocytes, etc
Interferon-beta (fibroblast
interferon)
- fibroblasts, epithelial cells,
etc
268. INDUCTION OF INTERFERON
interferon-alpha and interferon-
beta
- viral infection (especially RNA
viruses), double stranded RNA,
certain bacterial components
- strong anti-viral properties
interferon-gamma
- antigens, mitogenic stimulation
lymphocytes
269. INTERFERON
induces variety of proteins in target
cells
manyconsequences, not all fully
understood
271. interferon-alpha, interferon-beta
interferon receptor
induction of induction of induction of
2’5’oligo A synthase ribonuclease L protein kinase R (PKR)
ds RNA 2’5’oligo A ds RNA
activated activated activated
2’5’oligo A synthase ribonuclease L protein kinase R
ATP ATP
phosphorylated
2’5’oligo A
initiation factor (eIF-
2)
mRNA degraded inhibition of protein synthesi
273. OTHER EFFECTS OF
INTERFERONS
ALL TYPES
– INCREASE MHC I EXPRESSION
CYTOTOXIC T-CELLS
– ACTIVATE NK CELLS
CAN KILL VIRALLY INFECTED CELLS
274. OTHER EFFECTS OF
INTERFERONS
INTERFERON-GAMMA
– INCREASES MHC II EXPRESSION ON
APC
HELPER T-CELLS
– INCREASES ANTIVIRAL POTENTIAL OF
MACROPHAGES
INTRINSIC
EXTRINSIC
275. THERAPEUTIC USES OF
INTERFERONS
ANTI-VIRAL
– e.g. interferon-alpha is currently approved for
certain cases of acute and chronic HCV and
chronic HBV
MACROPHAGE ACTIVATION
– interferon-gamma has been tried for e.g.
lepromatous leprosy, leishmaniasis,
toxoplasmosis
ANTI-TUMOR
– have been used in e.g. melanoma, Kaposi‟s
sarcoma, CML
MULTIPLE SCLEROSIS
276. Viral response to host immune
system
Viruses may :
block interferon binding
inhibit function of interferon-induced
proteins
inhibit NK function
interfere with MHC I or MHC II expression
block complement activation
inhibit apoptosis
etc!
277. SIDE EFFECTS OF
INTERFERONS
FEVER
MALAISE
FATIGUE
MUSCLE PAINS
279. PROTECTION AGAINST
RE-INFECTION
IgG and IgA
– IgG less efficient but lasts longer
antibodies to both HA and NA
important
– antibody to HA more important (can
neutralize)
299. VACCINE
„BEST GUESS‟ OF MAIN ANTIGENIC
TYPES
– CURRENTLY
type A - H1N1
type A - H3N2
type B
each year choose which variant of each
subtype is the best to use for optimal
protection
300. VACCINE
inactivated
egg grown
some formulations licensed for
children
reassortant live vaccine approved
2003
– for healthy persons (those not at risk
for complications from influenza
infection) ages 5-49 years
309. STRUCTURAL FEATURES OF
ROTAVIRUS
60-80nm in size
Non-enveloped virus
EM appearance of a wheel with radiating
spokes
Icosahedral symmetry
Double capsid
Double stranded (ds) RNA in 11 segments
310. STRUCTURE
Double capsid (outer and inner
capsid)
Core with genome
Capsid is cleaved by trypsin to
form
ISVP- infective sub-viral particle
316. CLASSIFICATION
Groups- 7 Groups (A through G) based on VP6
differences
Group A is the most common and has 2
subgroups
317. CLASSIFICATION (contd.)
Serotypes based on viral capsid proteins
14 G serotypes based on G protein (VP 7)
differences
20 P serotypes based on P protein (VP4)
Common PG combinations are:-
P8G1, P8G2, P4G2, P8G4
318. CLASSIFICATION (contd.)
Electropherotypes are based on the mobility of
RNA segments by PAGE
Useful in epidemiologic studies
319. ROTAVIRUS- PROPERTIES
Virus is stable in the environment
Relatively resistant to handwashing
agents
Susceptible to disinfection with 95%
ethanol, „Lysol‟, formalin
320. PATHOGENESIS
Targeted host cells - mature enterocytes
lining the tips of intestinal villi
Intermediate/infective sub-viral particle
(ISVP) produced through proteolysis
Enter host cell by endocytosis
Virus replicates in the host cell cytoplasm
321. REPLICATION
mRNA transcription with viral RNA
polymerase
Capsid proteins formed
mRNA segments formed, assembled into
immature capsid
mRNA replicated to form double stranded
RNA genome
322. HISTOPATHOLOGY
Mature enterocytes lining the tips of
intestinal villi are affected
Villous atrophy and blunting
Death of the mature enterocytes
323. HISTOPATHOLOGY
Infiltration of lamina propria with
mononuclear cells
Repopulation of the villous tips with
immature secretory cells [crypt
hyperplasia]
325. EPIDEMIOLOGY
A major cause of diarrhea-
associated hospitalizations and
deaths
Seroprevalence studies show that
antibody is present in most by age
3y.
328. EPIDEMIOLOGY - USA
2.7- 3.5 million affected each year
Physician visits ~ 500,000/year
50,000-70,000 hospitalizations/year
20-40 deaths/year
Cases with dehydration ~ 1-2.5%
Economic impact
329. EPIDEMIOLOGY
Age- 4mo - 2 years
Protection of younger infants through
through transplacental antibody transfer
Asymptomatic infections are common,
especially in adults
Nosocomial infections
Outbreaks
Severe Disease young,
immunocompromised
330. Epidemiology (contd.)
Seasonality
Winter months (Nov. through May in US)
Gradual spread W to E
Year-round in the tropics
Incubation period - thought to be <4
days
333. TRANSMISSION
Mainly person to person via fecal-oral
route
Fomites
Foodand water-borne spread is
possible
Spreadvia respiratory route is
speculated
334. EPIDEMIOLOGY -
spread
Contagious from before onset of diarrhea
to a few days after end of diarrhea
Large amounts of viral particles are shed
in diarrheal stools
Infective dose is only 10-100 pfu
335. EPIDEMIOLOGY
Differences in Groups
Group A infections are most common
Group B has been associated with
outbreaks in adults in China
Group C is responsible for sporadic
cases of diarrhea in infants around
the world
336. CLINICAL CASE
A 22 month old female is admitted to the
pediatric ward for cough and fever up to 103 F.
Chest X ray shows left lower lobe pneumonia.
She is being treated with intravenous Ceftriaxone
and her fever is gradually improving.
On hospital day #5, she develops diarrhea with 4
watery stools and a fever of 102 F.
Stool studies showed no traces of blood and no
fecal leukocytes.
Further studies are pending.
337. CLINICAL FEATURES
Incubation period - thought to be <4 days
Fever- can be high grade (>102 F in 30%)
Vomiting, nausea precede diarrhea
Diarrhea
• usually watery (no blood or leukocytes)
• lasts 3-9 days
• longer in malnourished and immune deficient individuals.
• NEC and hemorrhagic GE seen in neonates
338. MECHANISM OF DIARRHEA
Watery diarrhea due to net secretion of
intestinal fluid
Activation of the enteric nervous system
Role of NSP4 peptide regions as an
enterotoxin
339. CLINICAL FEATURES
(contd.)
Dehydration is the main
contributor to mortality.
Secondary malabsorption of
lactose and fat, and chronic
diarrhea are possible
340. DIAGNOSIS
Antigen detection in stool by ELISA, LA
(for Group A rotavirus)
EM- non-Group A viruses also
Culture- Group A rotaviruses can be
cultured in monkey kidney cells
Serology for epidemiologic studies
341. TREATMENT AND
PREVENTION
Treatment
Supportive- oral, IV rehydration
Prevention
Handwashing and disinfection of
surfaces
342. VACCINE
Live tetravalent rhesus-human reassortant
vaccine (Rotashield)
Licensed for use in August 1998
Removed from the market in October 1999
due to risk of intussusception
Cases were seen 3-20 days after
vaccination
Approx. 15 cases/1.5 million doses
343. NEWER VACCINES
Rotarix Rota Teq
Monovalent G1P8 oral Pentavalent Human-
vaccine bovine reassortant
vaccine
Efficacy for prevention Efficacy for prevention
of severe disease = of severe disease =
85% 100%
346. Diarrhea due to
Enteric Adenovirus
Age <4 years
Year round
Spread via fecal-oral route
347. CLINICAL FEATURES-
Adenovirus gastroenteritis
Incubation period 3 -10 days
Diarrhea lasts for 10 -14 days
Can also cause intussusception,
mesenteric adenitis, appendicitis
348. DIAGNOSIS
Enteric adenoviruses
Isolation
requires special media-
Graham 293
ELISA for rapid detection is
available
357. CLINICAL FEATURES
Usual incubation Period is <24
hours
(ranges from 12hrs. to 4 days)
Short duration of illness <3 days
Nausea, vomiting, fever, headache
Abdominal cramping
Watery diarrhea
358. EPIDEMIOLOGY - Noroviruses
Worldwide distribution
>23 million cases/year in the U.S.
Major cause of foodborne
outbreaks of GE (>50%)
Most people have had infections by
age 4 years (by seroprevalence
studies)
359. SPREAD
Person-to-person Fecal-oral
spread (stool/vomitus)
Fecal contamination of food or
water
Spread through fomites
(stool/vomitus)
360. SPREAD- Viability of
Caliciviruses
Survive in water chlorinated at
routine levels (up to 10 ppm)
Survive freezing, heating up to
60 C
Evidently survive in steamed
shellfish
362. EPIDEMIOLOGY : Outbreaks
Cruise ships, schools, nursing
homes,
Can involve infants and school-age
children
Source usually is contaminated food
and water (E.g. seafood-oyster and
shellfish, salads, cake icing, raw fruit
etc.)
Rapid secondary spread
363. DIAGNOSIS
Specimen- stool, vomitus,
environmental swabs (during outbreak
investigations)
RT-PCR in state public health labs.
Serology for epidemiologic purposes
Immune EM is less used
365. ASTROVIRUS
Described in relation to an outbreak of
gastroenteritis in 1975
Detected by EM
Immunologically distinct from Human
Caliciviruses
Belong to family Astroviridae
8 human serotypes are known
