INFLUENZA: seasonal, avian
and pandemic
Current Situation - Potential for Pandemic
Avian Influenza A H5N1
The current widespread outbreaks in poultry of highly pathogenic avian influenza
caused by influenza A (H5N1) are unprecedented in scale. Never before in
the history of this disease have so many countries been simultaneously
affected, resulting in the loss of so many birds. An estimated 150
million birds have been killed by the virus or culled to prevent its
spread, from December 2003 to late 2005.
The prospect of a pandemic caused by H5N1 virus
was first seen in 1996
in Hong Kong when the virus emerged infecting poultry
and first infected humans in 1997. Mass
slaughter of poultry eliminated that virus from Hong Kong. However, it
is likely that the virus (which probably originated in South China continued to circulate there).
Progress of Avian Influenza H5N1 Virus
In February 2003, there was a report of a family from Hong Kong, who
were infected while visiting Fujian province in China, and two of the
family died. More...
H5N1 Birds to Human:
H5N1 is now enzootic in birds across Asia, and has spread to Europe and Africa. The virus may be at the threshold of jumping the species barrier as it has already caused over 165 (to Feb 2006) WHO collaborating laboratory-confirmed H5N1 infections in people. Over half of them have died. Furthermore the currently circulating strains of H5 virus are becoming more capable of causing disease for birds and mammals than earlier H5 viruses. Although there have been outbreaks of H5N1 in 17 countries, so far confirmed human cases have been restricted to only seven countries: Cambodia, China, Indonesia, Iraq, Thailand, Turkey and Viet Nam.
Get the latest data on confirmed cases reported to WHO at: http://www.who.int/csr/disease/avian_influenza/country/en/index.html
Human to Human spread of H5N1
There have been occasional reports suggestive of human-to-human transmission.
However, it is not certain that the cases might not have been
directly infected from birds. Furthermore, there has definitely not
been more than one generation of spread of the virus in humans. Studies
in healthcare workers have also not found evidence of spread.
This pattern shows that the current virus is not (yet) adapted to human spread. Nearly all confirmed cases have had intense and close contact with sick poultry or their droppings.
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