29 September 2004

Human cases of avian influenza

Further human cases of H5N1 avian influenza have been reported from Vietnam and Thailand following the resurgence of highly pathogenic avian influenza (HPAI) in poultry in China and south east Asia in July of this year.

On 28 September 2004, the WHO confirmed two cases of H5N1 avian influenza from a family cluster in Thailand. The cases are a 26-year-old woman who died on 20 September, and her 32-year-old sister, who remains hospitalised in a stable condition. WHO Avian influenza - situation in Thailand

The initial case in the cluster was an 11-year-old girl who died of pneumonia on 8 September 2004. No samples for diagnostic testing were obtained from her. She is known to have been in contact with sick and dead poultry and has been classified as a probable case of avian influenza by the Thai authorities. Her aunt, with whom the girl lived in the northern Thai province of Kamphaeng Phet, is confirmed to have H5N1 avian influenza but is recovering. Her mother, who lived in the Bangkok area, became ill and died on 20 September and has also been confirmed to have had H5N1 avian influenza. The family cluster also includes the 6-year-old son of the aunt of the initial case. He was hospitalised but is recovering, and samples are being tested. Although details are still being evaluated, it appears that the girl's mother had no contact with sick or dead poultry, but prior to her becoming ill, had cared for her daughter during her hospitalisation. This raises the possibility of human-to-human transmission from the girl to her mother.

Limited, un-sustained human-to-human transmission has been known to occur in previous outbreaks of human avian influenza. (1,2) The occurrence of human-to-human transmission is of concern since it could signal establishment of avian influenza in humans and lead to an influenza pandemic. The WHO along with the Ministry of Public Health in Thailand is actively investigating this possibility.

These cases bring the total number of confirmed deaths from avian influenza to 30; 10 in Thailand and 20 in Vietnam. There have been a total of 42 confirmed cases in these two countries, the only countries to report human cases in the current outbreak.

In addition to these human cases, outbreaks of HPAI in poultry continue to be reported in China and south east Asia. An outbreak has occurred amongst chickens at a farm in Kandal province, ; these Cambodia are the first cases of the disease in Cambodia following the outbreak in Asia earlier this year ( http://www.oie.int/eng/info/hebdo/aIS_26.htm#Sec7 ). Outbreaks of type H5 avian influenza have also been reported from peninsular Malaysia, the first such reports from Malaysia ( http://www.oie.int/eng/info/hebdo/aIS_27.htm#Sec5 ).

The risk of contracting avian influenza during travel is extremely low and there continue to be no travel restrictions. However, travellers going to China and south-east Asia are reminded of precautions recommended in previous postings:

• Avoid visiting live animal markets and poultry farms
• Avoid contact with surfaces contaminated with animal faeces
• Do not attempt to bring any live poultry products back to the UK

Travellers who return from affected areas and have respiratory symptoms should seek prompt medical attention.

References:

1. Katz JM, Lim W, Bridges CB, et al. Antibody response in individuals infected with avian influenza A (H5N1) viruses and detection of anti-H5 antibody among household and social contacts. J Infect Dis 1999;180:1763-1770.
2. Buxton Bridges C, Katz JM, Seto WH, et al. Risk of influenza A (H5N1) infection among health care workers exposed to patients with influenza A (H5N1), Hong Kong. J Infect Dis 2000;181:344-348

Further information is available from:

World Health Organization: www.who.int/csr/disease/avian_influenza/en/

Health Protection Agency: http://www.hpa.org.uk/webw/HPAweb&Page&
HPAwebAutoListName/Page/1160495617087

Centres for Disease Control and Prevention: www.cdc.gov/flu/avian/index.htm

World Organization for Animal Health: www.oie.int/eng/en_index.htm