The
global spread of highly pathogenic H5N1 in
birds is considered a significant
pandemic threat.
While other
H5N1 strains are known, they are significantly different from a current, highly pathogenic H5N1 strain on a genetic level, making the global spread of this new strain unprecedented. The H5N1 strain is a
fast-mutating, highly
pathogenic avian influenza virus (HPAI) found in multiple bird species. It is both epizootic (an epidemic in non-humans) and panzootic (a disease affecting animals of many species especially over a wide area). Unless otherwise indicated, "H5N1" in this article refers to the recent highly pathogenic strain of H5N1.
"Since
1997, studies of H5N1 indicate that these viruses continue to evolve, with changes in antigenicity and internal
gene constellations; an expanded host range in avian species and the ability to infect
felids; enhanced pathogenicity in experimentally infected
mice and ferrets, in which they cause systemic infections; and increased environmental stability."
[1]
Cumulate Human Cases of and Deaths from H5N1
As of
April 11,
2007
Notes:
Tens of millions of birds have died of
H5N1 influenza and hundreds of millions of birds have been slaughtered and disposed of, to limit the spread of H5N1. Countries that have reported one or more major highly pathogenic H5N1 outbreaks in birds (causing at least thousands but in some cases millions of dead birds) are (in order of first outbreak occurrence):
Korea,
Vietnam,
Japan,
Thailand,
Cambodia,
Laos,
Indonesia,
China,
Malaysia,
Russia,
Kazakhstan,
Mongolia,
Turkey,
Romania,
Croatia,
Ukraine,
Cyprus,
Iraq,
Nigeria,
Egypt,
India,
France,
Niger,
Bosnia,
Azerbaijan,
Albania,
Cameroon,
Myanmar,
Afghanistan,
Israel,
Pakistan,
Jordan,
Burkina Faso,
Germany,
Sudan,
Ivory Coast,
Djibouti,
Hungary,
United Kingdom,
Kuwait,
Bangladesh,
Saudi Arabia,
Ghana,
Czech Republic,
Togo.
Highly pathogenic H5N1 has been found in birds in the wild in numerous other countries:
Austria,
Bulgaria,
Denmark,
Greece,
Iran,
Italy,
Poland,
Serbia and Montenegro,
Slovakia,
Slovenia,
Spain,
Sweden,
Switzerland. Surveillance of
H5N1 in humans, poultry, wild birds, cats and other animals remains very weak in many parts of Asia and Africa. Much remains unknown about the exact extent of its spread.
H5N1 has low pathogenic varieties
endemic in
birds in North America. H5N1 has a highly pathogenic variety that is endemic in dozens of species of birds throughout south
Asia and is threatening to become endemic in birds in west Asia and
Africa. So far, it is very difficult for
humans to become infected with H5N1. The presence of highly pathogenic (deadly) H5N1 around the world in both birds in the wild (
swans,
magpies,
ducks,
geese,
pigeons,
eagles, etc.) and in
chickens and
turkeys on farms has been demonstrated in millions of cases with the
virus isolate actually
sequenced in hundreds of cases yielding definitive proof of the
evolution of this strain of this subtype of the species
Influenzavirus A (bird flu virus).
