Will the Avian Flu Become Will the Avian Flu Become the Next Epidemic?the Next Epidemic?

What is epidemiology?What is epidemiology?

The study of factors affecting the health and illness of The study of factors affecting the health and illness of populations.populations.

Endemic:Endemic: an infection is said to be " an infection is said to be "endemicendemic" in a human " in a human population when that infection is maintained in the population when that infection is maintained in the population without the need for external inputs. population without the need for external inputs.

Epidemic:Epidemic: is a classification of a disease that appears as is a classification of a disease that appears as new cases in a given human population, during a given new cases in a given human population, during a given period, at a rate that substantially exceeds what is period, at a rate that substantially exceeds what is "expected," based on recent experience."expected," based on recent experience.

Pandemic:Pandemic: is an epidemic that spreads through human is an epidemic that spreads through human populations across a large region (for example a continent), populations across a large region (for example a continent), or even worldwide.or even worldwide.

What is Influenza?What is Influenza?

There are three types of influenza There are three types of influenza viruses: A, B and C. viruses: A, B and C.

Influenza A and B viruses cause Influenza A and B viruses cause seasonal epidemics of disease almost seasonal epidemics of disease almost every winter in the United States. every winter in the United States.

Influenza type C infections cause a Influenza type C infections cause a mild respiratory illness and are not mild respiratory illness and are not thought to cause epidemics.thought to cause epidemics.

What is the Avian Flu?What is the Avian Flu?

Influenza A viruses are divided into Influenza A viruses are divided into subtypes based on two proteins on the subtypes based on two proteins on the surface of the virus: the surface of the virus: the hemagglutininhemagglutinin (H) and the (H) and the neuraminidase neuraminidase (N). (N).

There are 16 different hemagglutinin There are 16 different hemagglutinin subtypes and 9 different neuraminidase subtypes and 9 different neuraminidase subtypessubtypes

Influenza A viruses can be further Influenza A viruses can be further broken down into different strains. The broken down into different strains. The current subtypes of influenza A viruses current subtypes of influenza A viruses found in people are A (H1N1) and A found in people are A (H1N1) and A (H3N2).(H3N2).

How does the Avian Flu Virus How does the Avian Flu Virus (H5N1) Work?(H5N1) Work?

Neuraminidase: Neuraminidase: Helps virus bud Helps virus bud from host cell from host cell (reproduce)(reproduce)

HemagglutininHemagglutinin : : It is responsible It is responsible for binding the for binding the virus to the cell virus to the cell that is being that is being infected.infected.

How Does Avian Flu Spread?How Does Avian Flu Spread? Avian influenza, or “bird flu”, is a contagious Avian influenza, or “bird flu”, is a contagious

disease of animals caused by viruses that normally disease of animals caused by viruses that normally infect only birds and, less commonly, pigs. infect only birds and, less commonly, pigs.

Avian influenza viruses are highly species-specific, Avian influenza viruses are highly species-specific, but have, on rare occasions, crossed the species but have, on rare occasions, crossed the species barrier to infect humans.barrier to infect humans.

How can the Avian Flu “Jump” How can the Avian Flu “Jump” to Humans?to Humans?

Antigenic shiftAntigenic shift is is the process by the process by which two different which two different strains of influenza strains of influenza combine to form a combine to form a new subtype having new subtype having a mixture of the a mixture of the surface antigens of surface antigens of the two original the two original strains strains

How is it transmitted?How is it transmitted?

Through saliva, Through saliva, feces and bloodfeces and blood

Can last up to one Can last up to one week at body week at body temperature, one temperature, one month at zero month at zero degrees Celsius and degrees Celsius and does not degrade in does not degrade in arctic temperaturesarctic temperatures

What is the risk of What is the risk of pandemic?pandemic? The risk of pandemic influenza is serious. The risk of pandemic influenza is serious.

With the H5N1 virus now firmly entrenched in large parts of With the H5N1 virus now firmly entrenched in large parts of Asia, the risk that more human cases will occur will persist. Asia, the risk that more human cases will occur will persist.

Each additional human case gives the virus an opportunity Each additional human case gives the virus an opportunity to mutate and improve its transmissibility in humans, and to mutate and improve its transmissibility in humans, and thus develop into a pandemic strain. thus develop into a pandemic strain.

What signs have scientists What signs have scientists noticed?noticed?

Domestic ducks can now excrete large Domestic ducks can now excrete large quantities of highly pathogenic virus without quantities of highly pathogenic virus without showing signs of illness, and are now acting showing signs of illness, and are now acting as a “silent” reservoir of the virus as a “silent” reservoir of the virus

When compared with H5N1 viruses from When compared with H5N1 viruses from 1997 and early 2004, H5N1 viruses now 1997 and early 2004, H5N1 viruses now circulating are more lethal circulating are more lethal

H5N1 appears to have expanded its host H5N1 appears to have expanded its host range, infecting and killing mammalian range, infecting and killing mammalian species previously considered resistant to species previously considered resistant to infection with avian influenza viruses. infection with avian influenza viruses.

How can we prevent a How can we prevent a pandemic?pandemic?

The clock starts ticking when the first human gets The clock starts ticking when the first human gets the “new” virus.the “new” virus.

Work on a vaccine cannot start until the Work on a vaccine cannot start until the emergence of a new virus, and we predict it would emergence of a new virus, and we predict it would take six to nine months to develop it. take six to nine months to develop it.

The US, WHO and FAO have led global efforts to The US, WHO and FAO have led global efforts to encourage countries to heighten surveillance for encourage countries to heighten surveillance for outbreaks in poultry and significant numbers of outbreaks in poultry and significant numbers of deaths in migratory birds and to rapidly introduce deaths in migratory birds and to rapidly introduce containmentcontainment measures. measures.