WHO calms fears over human-to-human bird flu


By Jonathan Fowler GENEVA, AP

The World Health Organization on Tuesday downplayed concerns over human-to-human transmission of bird flu, after authorities in Thailand confirmed that a woman who died of the virus probably contracted it from her daughter.

But countries must remain vigilant because lab tests could show that the deadly H5N1 virus has mutated, said Klaus Stohr, head of WHO’s global influenza program. That would increase its chances of leaping the species barrier on a wider scale and raise the specter of a pandemic.

Scientists fear a global outbreak if the virus mutates to mix with human influenza to create a form that could easily jump from one human to another, said Stohr.

“In the past, the H5N1 virus has always been transmitted from poultry to humans,” Stohr told reporters.

“What is less well-known is that in the past there has also been some inefficient, unsustained, dead-end-street transmission between humans,” he said, referring to cases where the virus jumped from one person to another but was defeated by the second person’s antibodies before it managed to spread any further.

A bird flu outbreak in Hong Kong in 1997 killed six people and resulted in limited human-to-human transmission. Those who got the disease from other people experienced only minor symptoms, and there was no evidence the virus had mutated into a highly dangerous form.

Initial research suggests the latest Thai cases also fall into the “dead-end-street” category, Stohr said.

Nineteen human fatalities also were reported in Vietnam this year, and tens of millions of chickens and other poultry have been killed by the disease or culled to curb its spread through much of eastern Asia.

Most human cases have been traced to contact with sick birds. Human-to-human transmission was suspected in some Vietnamese cases, but never confirmed.