Bird flu pandemic a real possibilty

May 18 2005

According to the the World Health Organization (WHO), the pattern of human bird flu infections in Vietnam suggests the H5N1 virus that causes the illness is evolving in ways that makes it more contagious.

Vietnam, the nation hit hardest by the disease, has recorded 68 cases of bird flu in humans between late 2003 and the end of April. Two more human cases have been recorded since then by Vietnamese health authorities, though not yet confirmed by the United Nations health agency. At least 36 Vietnamese have died after contracting the H5N1 bird-flu virus.

In a review of bird-flu cases, the WHO says a wider age range of people are being infected but there are fewer deaths from the disease, and it is possible that the changes demonstrate that H5N1 viruses are becoming more capable of human-to-human transmission.

The WHO says the avian H5N1 viruses are continuing to evolve and pose a potential pandemic threat, and it is possible that the viruses are becoming more infectious for people.There are however some epidemiological differences between the two outbreaks reported since the end of last year.

Vietnamese health authorities have this year reported cases in a health-care worker and in at least four sets of family members, and investigators are concerned that change in the pattern of the disease raises the possibility that transmission between humans has occurred.

Three asymptomatic infections were documented among close contacts of confirmed cases, suggesting the presence of milder degrees of infection.

Jeremy Farrar, director of the University of Oxford Clinical Research Unit at the Hospital for Tropical Diseases in Ho Chi Minh City, says if this is proved to be the case it is not very reassuring, because it could mean that the virus has become a little less virulent in people, and is circulating in a wider pool of people. He says this means that there is a greater chance of the virus resorting with a human flu virus or mutating into a virus of pandemic potential.

The average age of people infected in northern Vietnam has increased to 31 from 17.

A 52-year-old man from the northern province of Vinh Phuc and a 58-year-old man from the northern province of Thanh Hoa have tested positive for bird flu this week, according to Nguyen Duc Hien, director of the Institute for Clinical Research in Tropical Medicine in Hanoi. The cases are the first two recorded in Vietnam since mid-April.

The WHO report says it is unlikely the new epidemiological patterns were random variation, and the changes were consistent with the avian virus possibly adapting to a human host.