Bird flu could threaten humans worldwide - study

A type of bird flu that has killed millions of chickens is becoming more infectious to mammals.

Scientists fear it could cause the next worldwide pandemic in humans.

The avian flu has forced authorities to slaughter millions of chickens and other fowl in Asia to stem outbreaks in recent years. Thousands more have been killed in the United States and elsewhere.

Already the flu has passed from birds to humans in Hong Kong, killing six of 18 people infected in 1997, and human cases have been reported since then in Vietnam and Thailand.

Now China-based researchers studying the H5N1 strain of the flu report that it has been changing over the years to become more dangerous to mammals.

Their research, based on tests in mice, is reported Proceedings of the National Academy of Sciences.

“Our results demonstrate that while circulating in domestic ducks, H5N1 viruses gradually acquired the characteristics that make them lethal in mice,” reported the team, led by Hualan Chen of the Animal Influenza Laboratory of the Chinese Ministry of Agriculture.

Human infections from bird flu remain rare, but the World Health Organisation considers it a potential major threat.

Two possibilities exist for the bird virus becoming a serious danger to people.

Viruses constantly mutate, and this one could accumulate enough genetic changes to become good at passing between humans. So far human cases have derived from birds, and no evidence has arisen of the bird flu being passed from person to person.

Even more worrisome, the experts say, would be sudden change that could be caused should the flu combine with a human flu in someone’s body. The two viruses could swap genes and create a potent hybrid as deadly as the bird strain and as contagious as a regular human strain.