History of HPAI occurrence in the world

HPAI has been recognized for well over one hundred years, and it seems clear that for the first third of the twentieth century the virulent disease was endemic in some countries and occurred fairly regularly in others. Since the first report of an HPAI outbreak caused by a virus of H5 subtype, in 1959, primary outbreaks of HPAI in poultry have been reported several times. The outbreaks have been caused by influenza A viruses of either H7 or H5 subtype. Barring the recent crisis, most of the previous outbreaks have shown very limited spread, some, such as that in the United Kingdom (England) in 1991, being self-limiting to a single flock of birds. However, in the United States of America in 1983 and Pakistan in 1995, the disease became widespread, infecting many flocks and causing enormous losses both economic and in the number of birds that died or were slaughtered as part of control policies. In 1997, a highly pathogenic H5N1 avian influenza virus caused serious disease in both people and poultry in China, Hong Kong Special Administrative Region. Eighteen human cases of disease were recorded, six of which were fatal. This unique virus was eliminated through total depopulation of all poultry markets and chicken farms in December 1997. Other outbreaks of HPAI caused by H5N1 viruses occurred in poultry in 2001 and 2002. These H5N1 viruses isolated had different internal gene constellations from those isolated in 1997. Since 1995 there have been several outbreaks of AI in Pakistan. Outbreaks were reported of HPAI type A, subtype H7N3, in 1995 and 2003 and low pathogenic avian influenza (LPAI) type A, subtype H9N2, in 1998. Outbreaks of a highly pathogenic strain of avian influenza virus A (subtype H7N7) have been reported in various poultry farms in the Netherlands since February 2003 with one death and more than 80 cases of mild disease in humans. Recent cases of the disease in poultry have also been reported in Belgium.

Outbreaks of HPAI virus type A reported in poultry, 1959 to 2004

¹ Former German Democratic Republic (GDR).

² See Table, page 17.

Bibliography

Alexander, D.J. 2000. A review of avian influenza in different bird species. Vet. Microbiol., 74(1-2): 3-13.

FAO. 2004. Consultant mission reports.

Sims, L.D., Ellis, T.M., Liu, K.K., Dyrting, K., Wong, H., Peiris, M., Guan, Y. & Shortridge, K.F. 2003. Avian influenza in Hong Kong 1997-2002. Avian Dis., 47(3 Suppl.): 832-838.

World Health Organization (WHO) Web site (http://www.who.int/en/).

World Organisation for Animal Health (OIE) Web site (http://www.oie.int/eng/en_index.htm).