Modules:
1. Introduction
2. Influenza Viruses
3. Seasonal, Avian, and Pandemic Influenza
4. Influenza: the disease
5. New Zealand pandemic planning
6. Primary Health Care preparedness
7. Community preparedness
8. Anti-viral Drugs
9. Vaccines
10. Common Questions
11. Resources
12. Course Conclusion

 

Risk in NZ:
If avian H5N1 enters NZ via an infected bird there is little direct human health threat as long as the virus does not establish itself in bird populations in NZ. More...

 

No Current Risk in NZ Birds:
It is also important to emphasise that, at present, the H5N1 virus does not pose a threat to human health - except in those who have contact with sick birds in the countries affected.

There are no birds infected with H5N1 in New Zealand currently.

 

 

INFLUENZA: seasonal, avian
and pandemic

Influenza Pandemics

A pandemic, a global epidemic, arises when a new sub type of influenza A arises via antigenic shift. This new sub-type displaces the previously circulating influenza type A virus and becomes the seasonal influenza virus that continues circulating until the next pandemic.

Since 1510 there have been an average of three influenza pandemics per century that are historically documented.

Ref: Ghendon Y. Introduction to pandemic influenza through history. Eur J Epidemiol. 1994 Aug;10(4):451-3.

In the 20th century, there were three influenza pandemics: Starting in 1918 ("Spanish Flu"), 1957 ("Asian Flu") and 1968 ("Hong Kong Flu").

In 1977, there was a re-emergence of the HIN1 virus ("Russian Flu"), but it did not replace the H3N2 sub type.

With the population explosion, both in humans and in domesticated birds that has occurred through the last century and changed animal husbandry practices and the industrialisation of the production of animal protein, there are more opportunities than ever for mixing of avian and human influenza viruses to lead to the emergence of a new influenza A subtype.

Another potential 'mixing vessel' for human and avian influenza viruses is the pig that can act as host to both types of virus. This is why it is speculated that the 1957 and 1968 pandemics (caused by a combination ["reassortment"] of avian and human influenza viruses originated in a pig).

The 1918 Pandemic:

The 1918 virus (H1N1) is inappropriately called the "Spanish Flu" as it most likely originated in the USA [in January 1918, Haskell County, Kansas according to JM Barry in "The Great Influenza. Penguin, 2005"]. More...

1957 and 1968 Pandemics:

The viruses causing the 1957 ("Asian Flu", H2N2) and 1968 ("Hong Kong Flu", H3N2) pandemics are both believe to have originated in Asia. There is good genetic evidence that both these viruses were re-assortments: Viruses that had been generated from mixing of human and influenza viruses. More...

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