Seasonal Influenza and Swine-Origin Influenza A (H1N1) Virus

1. Seasonal Influenza and Swine-Origin Influenza A (H1N1) Virus

2. Part One Seasonal Influenza

3. Influenza Viruses Classified into types A, B, and C Types A and B cause significant disease worldwide Types B and C limited to humans Type A viruses More virulent Wild waterfowl reservoir Affect many species Photo: Cynthia Goldsmith, CDC 3

4. Influenza A Viruses Categorized by subtype Classified according to two surface proteins Hemagglutinin (HA) – 16 known subtypes Site of attachment to host cells Antibody to HA is protective Neuraminidase (NA) – 9 known subtypes Helps release virions from cells Antibody to NA can help modify disease severity Hemagglutinin This image is in the public domain in the United States 4

5. Influenza A HA and NA Subtypes Other Animals Other Animals Other Animals Other Animals Other Animals Other Animals 5

6. Seasonal Influenza Transmission Routes U.S. Centers for Disease Control and Prevention • Influenza is an acute respiratory disease • Signs and symptoms reflect respiratory route • Fever, cough, headache, muscle aches • Sometimes lower respiratory • Transmission of influenza viruses • Person-to-person through droplets from coughing or sneezing • Transmission from objects (fomites) possible • Infectious 1 day before and up to 7 days after becoming sick 6

7. Seasonal Influenza Communicability U.S. Centers for Disease Control and Prevention Viral shedding can begin 1 day before symptom onset Peak shedding first 3 days of illness Subsides usually by 5-7th day in adults Infants, children and the immunosuppressed may shed virus longer 7

8. Human Influenza Clinical Diagnosis U.S. Centers for Disease Control and Prevention • Clinical symptoms non-specific • Symptoms overlap with many pathogens • Couple with laboratory data to verify diagnosis • Even during peak seasonal influenza activity, only about 30% specimens tested for influenza are positive in the United States 8

9. Human Influenza Complications U.S. Centers for Disease Control and Prevention • Sinus and ear infections • Viral and bacterial pneumonia • Myocarditis and Pericarditis • Myositis • Encephalopathy and encephalitis • Febrile seizures • Worsening of underlying chronic conditions • Sepsis-like syndrome in infants 9

10. Part Two Swine-Origin Influenza Virus (S-OIV)

11. April 2009 Swine-Origin Influenza A (H1N1) Virus (S-OIV) • The strain currently circulating is a novel Influenza A(H1N1) • It is thought to be composed of avian, human, and swine components from various continents • This strain is most likely a new subtype of A/H1N1 not previously seen in swine or humans • The strains isolated in the US and Mexico appear to be identical

12. General S-OIV Information • There are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1 • Swine-origin influenza viruses have high attack rates and low death rates in pigs • Swine-origin influenza viruses do NOT typically infect humans – until this outbreak, there had been 12 cases in the US since December 2005, with no deaths

13. Food Safety • You cannot contract swine-origin influenza from eating pork or pork products. • Eating properly handled and cooked pork products is safe. Cooking pork to an internal temperature of 160°F kills the swine-origin influenza virus as it does other bacteria and viruses.

14. Transmission of S-OIV • Human transmission of swine-origin influenza and seasonal influenza viruses is thought to occur in the same way • Transmission can occur via: • Contact with secretions from persons infected with swine influenza virus • Contact with infected pigs or environments (surfaces, objects) contaminated with the virus

15. Human infection with S-OIV • Symptoms may include: • Fever, cough, headache, muscle aches (similar to seasonal influenza) • Some people reported diarrhea, nausea and vomiting • Symptom onset begins 1-5 days after exposure • Infected individuals can spread the virus as long as they are symptomatic (or at least 7 days following illness onset)

16. Case Definitions • Suspect Case: a person with acute febrile respiratory illness with onset • within 7 days of close contact with a person who is a confirmed case of S-OIV infection, or • within 7 days of travel to community either within the United States or internationally where there are one or more confirmed cases of S-OIV infection, or • resides in a community where there are one or more confirmed cases of S-OIV infection. • Probable Case: a person with an acute febrile respiratory illness who is positive for influenza A, but negative for H1 and H3 by influenza RT-PCR • Confirmed Case: a person with an acute febrile respiratory illness with laboratory confirmed S-OIV infection at CDC by one or more of the following tests: • real-time RT-PCR • viral culture

17. Treatment of S-OIV • The CDC recommends Oseltamivir (Tamiflu) and Zanamivir (Relenza) for treatment • Oseltamivir is approved to treat and prevent infection in people at least 1 year old • Zanamivir is approved to treat infection in people at least 7 years old, and to prevent infection in people at least 5 years old • Antiviral drugs are most effective within 2 days of symptom onset • There is currently NO vaccine available for swine influenza but it is anticipated that one will be developed in the next few months

18. Part Three Pandemics

19. Requirements for an Influenza Pandemic Virus • A new influenza A subtype virus emerges that can infect humans AND • Causes serious illness AND • Spreads easily from human-to-human in a sustained manner 19

20. Pandemic Influenza Phases

21. Resources • http://PandemicFlu.gov • CDC’s Swine Flu Info Center: http://www.cdc.gov/swineflu/?s_cid=swineFlu_outbreak_001 • WHO’s Swine Flu Info Center http://www.who.int/csr/disease/swineflu/en/