WHO NEWS
Avian flu virus could evolve into dangerous human pathogen, experts fear
Fiona Fleck
Geneva
An unprecedented epidemic of avian influenza has affected huge populations of domestic and migratory birds across Asia triggering fears the virus could mutate into a dangerous human pathogen.
The bird flu strain, known as A (H5N1), has been reported in eight countries: Cambodia, China, Indonesia, Japan, Lao People's Democratic Republic, Republic of Korea, Thailand and Viet Nam among bird populations since mid-December 2003. As of 23 February 2004, there has been a total of 32 laboratory-confirmed human cases in the region of which 22 have died.
The United Nations Food and Agriculture Organization, World Organization for Animal Health and WHO proposed a control programme in January to help countries eradicate the disease calling for a mass cull of birds infected or exposed to the virus and called on international donors to help countries compensate farmers for the loss, described as a disaster for agricultural production.
"The real issue now is to avoid the emergence of a pandemic, and that means to eliminate the animal reservoir. And that should be done in a safe way so that persons are not going to be exposed to the virus without being protected," said Klaus Stohr, WHO project leader of the Influenza Surveillance and Scientific Groups for the H5N1 Influenza Outbreak.
Experts say this winter's epidemic could have serious implications because some H5N1 strains have proved to be infectious and capable of causing severe disease in humans. Unlike SARS, scientists have not yet found evidence of human-to-human transmission of H5N1. A field investigation in Viet Nam of a family cluster including two confirmed cases and an unexplained death due to acute respiratory illness found no conclusive evidence of human-to-human transmission but it has not yet been ruled out.
Apart from the immediate risk of transmission to humans who are in close contact with infected birds, the widespread presence of the virus across Asia increases the chances of co-infection with human and avian viruses and, potentially worse, could trigger the exchange of genes within viruses from other species creating a new, more lethal human virus.
"This is a serious global threat to human health," said WHO Secretary-General, Dr Lee Jong-Wook.
"We have faced several emerging infectious diseases in the past. This time, we face something we can possibly control before it reaches global proportions if we work cooperatively and share needed resources," said Lee.
Whilst diagnostic tests and expensive anti-viral medicines are available, there is not yet a vaccine for the virus. About a dozen pharmaceutical companies are working hard to develop one but success may be several years away.
Human cases of the virus have at present only been found in Viet Nam and Thailand. Viet Nam has suffered the most widespread avian flu outbreak among birds this winter as well as the highest number of human cases 15 of 23 people infected with the H5N1 virus have died.
In Thailand, a two-year-old boy from Suphanburi Province and a 27-year-old woman from Uttaridit Province recovered from bird flu earlier in February, but the other seven cases including a 13-year-old boy have died.
Most human cases were in direct contact with sick or dead birds, although no one involved in culling birds appears to have caught avian flu, WHO said. Avian flu is believed to have first jumped species from bird to man in 1997, when an outbreak of the disease caused by the A (H5N1) virus among birds triggered 18 human cases in Hong Kong Special Administrative Region of which 6 died.
WHO is conducting investigations into reports of H5N1 infection of domestic cats from a single household in Thailand. Fourteen out of the 15 cats have died, two of which have been reported infected with H5N1 by the Faculty of Veterinary Sciences at Thailand's Kasetsart University. According to WHO, confirmation of the virus in cats is not likely to enhance the present risks to human health.
First symptoms are fever, sore throat and cough, but the disease can lead also to hepatitis and even damage to the heart or kidneys.
For the latest information on avian flu, visit: http://www.who.int/csr/don/en/ 