1997 avian influenza outbreak

The 1997 avian influenza outbreak (also called "bird flu"), was a highly pathogenic avian influenza A(H5N1) outbreak known to be the first to be transmitted to humans. It occurred in Hong Kong in 1997, when humans started acquiring the virus directly from chickens, without the involvement of an intermediate host.[1]

Outbreak in non-human species

Epidemiologic and molecular evidence suggests that poultry was the source of the outbreak in humans. It began in March and April on chicken farms in Lau Fau Shan and Yuen Long, in the New Territories in the northwestern part of Hong Kong. The virus was identified as A(H5N1),[2] which exhibits high virulence in both avian and mammalian species, causing systemic infection in both chickens and mice.[3] After the outbreak was transmitted to humans, a territory-wide slaughter of more than 1.5 million chickens was conducted at the end of December.[1]

Outbreak in humans

In May 1997, the same virus (H5N1) was isolated from a 3-year-old boy in Hong Kong, who died of extensive influenza pneumonia complicated by Reye syndrome. After no new reported cases for 6 months, by the end of the year, a total of 18 cases of human influenza would be identified, all caused by the same virus.[3] These cases were scattered in different residential districts without apparent geographic clustering. 8 infected individuals were male, and 10 were female, with ages ranging from 1 to 60 years. One-half of the individuals were less than 12 years of age. Six of these individuals died, and 12 made a full recovery.[4] It is believed that most of the infected people contracted the virus directly from birds.[5][6]

Further spread

The A(H5N1) is unusually virulent in the human host, especially so in adults, therefore it was poorly transmissible from human-to-human, preventing it from acquiring pandemic properties.[2] However, the possibility of viral adaptation to the human species has been confirmed, given the ability of the virus to undergo variation due to mutations and reassortment. Since 1997, an increased circulation of highly pathogenic avian influenza has been consistently detected in poultry and wild birds in several countries. In December 2002 and January 2003, new outbreaks were reported in Hong Kong in poultry and wild birds. By the end of 2003 and beginning of 2004, multiple outbreaks were found in South Korea and Indonesia, then in Vietnam, Japan, Taiwan, Cambodia, Laos, Thailand and Mainland China.[6] The strain later spread to some areas of the Middle-East, Europe and Africa.[7] An additional 271 human cases of avian influenza (59.1% of them lethal) have been officially reported by the World Health Organization as of February 2007.[8]

See also

References
  1. Chan, PK (2002). "Outbreak of avian influenza A(H5N1) virus infection in Hong Kong in 1997". Clinical Infectious Diseases. 34: S58–S64. doi:10.1086/338820. PMID 11938498.
  2. Shortridge, K.F.; Peiris, J.S.M.; Guan, Y. (2003). "The next influenza pandemic: lessons from Hong Kong". Journal of Applied Microbiology. Hong Kong: Department of Microbiology, The University of Hong Kong. 94: 70–79. doi:10.1046/j.1365-2672.94.s1.8.x. PMID 12675938.
  3. Horimoto, Taisuke; Kawaoka, Yoshihiro (2001). "Pandemic Threat Posed by Avian Influenza A Viruses". Clinical Microbiology Reviews. 14: 129–149. doi:10.1128/CMR.14.1.129-149.2001. PMID 11148006.
  4. Chan, Paul K. S. (2002). "Outbreak of Avian Influenza A(H5N1) Virus Infection in Hong Kong in 1997". Clinical Infectious Diseases. 34: S58–S64. doi:10.1086/338820. PMID 11938498.
  5. "'Bird flu' death in Hong Kong raises fears". newscientist.com. Retrieved 2 April 2020.
  6. "AVIANinfluenza" (PDF). oie.int. Retrieved 1 April 2020.
  7. "Avian Influenza ("bird flu") fact sheet". health.nsw.gov.au. Retrieved 2 April 2020.
  8. Proença-Módena, José Luiz; Santos Macedo, Izolete; Arruda, Eurico. "H5N1 avian influenza virus: an overview". Brazilian Journal of Infectious Diseases. 11 (1): 125–133. doi:10.1590/S1413-86702007000100027. PMID 17625741.
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