Will the Avian Flu Become the Next Epidemic?

1. Will the Avian Flu Become the Next Epidemic?

2. What is epidemiology? • The study of factors affecting the health and illness of populations. • Endemic: an infection is said to be "endemic" in a human population when that infection is maintained in the population without the need for external inputs. • Epidemic: is a classification of a disease that appears as new cases in a given human population, during a given period, at a rate that substantially exceeds what is "expected," based on recent experience. • Pandemic: is an epidemic that spreads through human populations across a large region (for example a continent), or even worldwide.

3. What is Influenza? • There are three types of influenza viruses: A, B and C. • Influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. • Influenza type C infections cause a mild respiratory illness and are not thought to cause epidemics.

4. What is the Avian Flu? • Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N). • There are 16 different hemagglutinin subtypes and 9 different neuraminidase subtypes • Influenza A viruses can be further broken down into different strains. The current subtypes of influenza A viruses found in people are A (H1N1) and A (H3N2).

5. How does the Avian Flu Virus (H5N1) Work? • Neuraminidase: Helps virus bud from host cell (reproduce) • Hemagglutinin : It is responsible for binding the virus to the cell that is being infected.

6. How Does Avian Flu Spread? • Avian influenza, or “bird flu”, is a contagious disease of animals caused by viruses that normally infect only birds and, less commonly, pigs. • Avian influenza viruses are highly species-specific, but have, on rare occasions, crossed the species barrier to infect humans.

7. How can the Avian Flu “Jump” to Humans? • Antigenic shift is the process by which two different strains of influenza combine to form a new subtype having a mixture of the surface antigens of the two original strains

8. How is it transmitted? • Through saliva, feces and blood • Can last up to one week at body temperature, one month at zero degrees Celsius and does not degrade in arctic temperatures

9. What is the risk of pandemic? • The risk of pandemic influenza is serious. • With the H5N1 virus now firmly entrenched in large parts of Asia, the risk that more human cases will occur will persist. • Each additional human case gives the virus an opportunity to mutate and improve its transmissibility in humans, and thus develop into a pandemic strain.

10. What signs have scientists noticed? • Domestic ducks can now excrete large quantities of highly pathogenic virus without showing signs of illness, and are now acting as a “silent” reservoir of the virus • When compared with H5N1 viruses from 1997 and early 2004, H5N1 viruses now circulating are more lethal • H5N1 appears to have expanded its host range, infecting and killing mammalian species previously considered resistant to infection with avian influenza viruses.

11. How can we prevent a pandemic? • The clock starts ticking when the first human gets the “new” virus. • Work on a vaccine cannot start until the emergence of a new virus, and we predict it would take six to nine months to develop it. • The US, WHO and FAO have led global efforts to encourage countries to heighten surveillance for outbreaks in poultry and significant numbers of deaths in migratory birds and to rapidly introduce containment measures.