14 January 2004
Dear Doctor,
Outbreak of human H5N1 avian influenza in Vietnam
On 13 January 2004, the World Health Organization (WHO) has received laboratory confirmation of three cases of influenza (A/H5N1) avian influenza in humans in Hanoi region of Vietnam 这连结会以新视窗打开。 http://www.wpro.who.int/emerging_diseases/AvianInfluenza/en/index.html (WHO website). The samples came from two children and one adult who have since died. The source of infection is being investigated. The WHO has concluded that so far there was no evidence of human-to-human transmission. Concurrently H5N1 avian flu outbreaks among chickens have been reported from Korea and Japan in addition to Vietnam. The Department of Health (DH) is closely monitoring the situation.
Avian influenza (A/H5N1) was first known to infect humans in 1997 when 18 cases (including six deaths) were identified in Hong Kong, and two cases with one death in 2003. The available investigation results conducted in 1997 supported the view that the main mode of transmission was from bird to man, and that man-to-man transmission, although it could occur, was inefficient and rare. For more details, please make reference to the articles on avian influenza (A/H5N1) of the Public Health and Epidemiology Bulletin at 这连结会以新视窗打开。 http://www.chp.gov.hk/en/epidemiology/29/134/441/69.html .
Hong Kong has a sensitive and comprehensive influenza surveillance system. The sentinel surveillance shows low flu-like illness (ILI) activity in recent three weeks. There were no A/H5N1 isolates recently from our laboratory surveillance. Influenza activity in Hong Kong has been closely monitored and a weekly summary on influenza activity is available in the DH's website at 这连结会以新视窗打开。 http://www.chp.gov.hk/en/guideline1_year/29/134/441/304.html .
In view of the human cases of avian influenza H5N1 in Vietnam, such differential diagnosis should be considered in severe pneumonia cases with travel history to Vietnam during 7 days before symptom onset. History of live poultry contact should be asked. Please also advise patients travelling to places that report avian flu outbreaks: i) avoid contact with live poultry/birds, ii) wash hands thoroughly after contact with live poultry/birds, iii) consult a doctor if they develop symptoms of influenza while travelling.
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