1. Abbas Morovvati

3. Outline
1-Influenza Virus
2- Swine Influenza
3- Surface Proteins
4-Pandemic influenza
5-Influenza Pathogenesis

4. Influenza Virus
 Influenza: Highly infectious viral illness
 Virus was first isolated in 1933
 Single-stranded RNA virus
 Orthomyxoviridae family
 3 types: A, B, C
 Subtypes of type A determined by hemagglutinin (H)
and neuraminidase (N)

5. Swine Influenza
Type A Subtype H1N1
Type A - moderate to severe illness
- all age groups, potential for epidemic
- humans and other animal
Type B - milder disease
- primarily affects children
- humans only
Type C - rarely reported in humans
- no epidemics

6. Influenza Virus
Surface Proteins
haemagglutinin
neuraminidase

7. Antigenic Drift
 Gradual change in the virus with mutations and substitutions in
the amino acid chain of the surface proteins
(neuraminidase and haemagglutinin).
 A new strain can trigger a new epidemic
usually prevail for 2-5 years before next antigenic drift.

8. Antigenic Shift
 A type A influenza virus with a completely novel haemagglutinin or
neuraminidase formation moves into the human species from
other host species
 The primary source is birds, with recombination in swine or
humans.

10. Pandemic influenza
 The fact is, that flu is one of the most formidable infections
confronting humankind. The virus mutates constantly as it
circulates among birds, pigs and humans. So each new flu
season brings new challenges
 First pandemic known in 15th century
 In pandemic response and planning, prediction of the future
is not possible. Thought is to hope for best, but plan for
worst

11. Recent Pandemics
 1889-1890 – first recorded pandemic
 1918 ―Spanish‖ flu- 20-40 million deaths
 1957 ―Asian‖ flu- 1 million deaths
 1968 ―Hong Kong‖ flu- 1 million deaths
 1976 ―Swine‖ flu – unreported deaths

13. Influenza Pathogenesis
 Respiratory transmission of virus
 Replication in respiratory epithelium
with subsequent destruction of cells
 Viremia rarely documented
 Viral shedding in respiratory secretions
for 5-10 days

14. Symptoms of influenza include:
– Fever
– Cough
– Headache
– Myalgia
– Fatigue and weakness
– Chest discomfort
– Nausea, diarrhea with swine flu

15. Risk factors for complications:
 Age > 65 years
 Residence of nursing homes and other
chronic care facilities
 Chronic cardiac or pulmonary disorders
 Chronic conditions such as diabetes
 Long term ASA therapy
 Immunosuppression

16. Diagnosis
 Symptoms of cough and fever has a
 30%– 40 % predictive power.
 Symptoms with surveillance (flu in
community) has a 70% - 80% predictive
power.

17. Current Pandemic Influenza Phase (as of June 15, 2009): Phase 6

18. World Health Organization Pandemic Influenza Phases (2009)
Pandemic Influenza
Phase Characterization of Phase Public Health Goals
Ensure rapid characterization of the
Human infection(s) with a new subtype, but no human-
new virus subtype and early detection,
Phase 3 to-human spread, or at most rare instances of spread
notification and response to additional
to a close contact
cases
Contain the new virus within limited foci
Small cluster(s) with limited human-to-human
or delay spread to gain time to
Phase 4 transmission but spread is highly localized, suggesting
implement preparedness measures,
that the virus is not well adapted to human
including vaccine development
Larger cluster(s) but human-to-human spread still Maximize efforts to contain or delay
localized, suggesting that the virus is becoming spread, to possibly avert a pandemic,
Phase 5
increasingly better adapted to humans, but may not yet and to gain time to implement pandemic
be fully transmissible (substantial pandemic risk) response measures
Pandemic increased and sustained transmission in
Phase 6 Minimize the impact of the pandemic
general population

19. How does novel H1N1 Influenza
spread?
 This virus is thought to spread the
 same way seasonal flu spreads
 • Primarily through respiratory
 droplets
 • Coughing
 • Sneezing
 • Touching respiratory droplets on
 yourself, another person, or an
 object, then touching mucus
 membranes (e.g., mouth, nose,
 eyes) without washing hands

20. Persons at High Risk
 Persons at increased risk of severe illness from influenza include: people older
than 65 years, children younger than five years,
 pregnant women, and people of any age with certain chronic medical conditions,
like diabetes, asthma, immune-suppression, or
 chronic lung disease. See Interim Recommendations for Facemask and
Respirator Use to Reduce Novel Influenza A (H1N1) Virus
 Transmission
 􀁺 Information on care of certain groups at increased risk of severe illness from
influenza can be found at the following links.
 􀁺 Pregnant Women and Novel Influenza A (H1N1) Considerations for
Clinicians
 􀁺 H1N1 Flu and Patients With Cardiovascular Disease (Heart Disease and
Stroke)
 􀁺 Interim Guidance—HIV-Infected Adults and Adolescents: Considerations for
Clinicians Regarding Novel Influenza A
 (H1N1) Virus