Table 1. Key observed changes in epidemiological characteristics of the H5N1 HPAI virus.
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|
Year |
Reported changes in virulence, infectivity, or environmental resilience of H5N1 HPAI virus |
| |
1996 |
pathogenic H5N1 outbreak recorded from domestic geese in southern China
(Webster et al. 2006) |
1997 |
duck H5N1 reassorts with quail H9N2, becomes highly pathogenic strain (Guan
et al. 2000); acquires capability for causing fatal disease in humans, and human-to-human
transmission (Tam 2002) |
1999 |
NS genes of post 1998-strains enhance virus replication in mammalian cells
(Twu et al. 2007);
increased lethality in mammals demonstrated by laboratory trials in mice
(Guan et al. 2002) |
2000 |
infectivity for domestic ducks increased, although domestic ducks remain
asymptomatic carriers (Li et al. 2004) |
2001 |
increase in infection duration and length of virus shedding period in
domestic ducks (Hulse-Post et al. 2005);
increased virulence in mammals (Lipatov et al. 2003);
infections among swine discovered in Fujian, China (Shu et al.
2006) |
2002 |
acquires capability to cause fatal disease in wild and domestic ducks
(Sturm-Ramirez et al. 2004);
further increased infectivity to mammals (Chen et al. 2004);
fatal infections of tigers and cats recorded in China (Xia et al.
2003). |
2003 |
decreased environmental stability in water (Brown et al. 2007);
fatal infections of tigers and leopards in Thailand (Keawcharoen at al.
2004) |
2004 |
further increased lethality in mammals and
humans (Maines et al. 2005);
case rate mortalities of 70-80% recorded for
confirmed human H5N1 cases in Vietnam and Thailand (Tran et al. 2004,
Areechokchai at al. 2006) |
2005 |
oseltamivir resistant strain emerges in Vietnam
(de Jong et al. 2005);
amantadine/rimantadine resistant H5N1 strain
recorded in northern China (He at al. 2007);
H5N1 infections of village swine documented in
Indonesia (Cyranoski 2005) |
2006 |
vaccine-resistant “Fujian strain” attains dominance in
China (Smith et al. 2006);
first human H5N1 cases reported from Europe, Central Asia, Africa, and the
Middle East (Turkey, Iraq, Azerbaijan, Egypt, Djibouti: WHO 2008) |
2007 |
oseltamivir-resistant strain emerges in Egypt (WHO 2007);
H5N1 infections detected among vaccinated poultry in Egypt (WHO 2008a) |
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