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Bird Flu Virus Mutations Found in Turkish Sample

Posted on: Monday, 23 January 2006, 06:00 CST

By Anita Manning

Mutations that could make it easier for the bird flu virus to infect humans have been found in a sample taken from a patient in Turkey, a report in the journal Nature said Friday.

The World Health Organization is monitoring the situation, but a spokeswoman said it is too early to know whether the virus is changing in ways that would signal the start of a human flu pandemic.

"It's one isolate from a single virus from Turkey," WHO's Maria Cheng said in Geneva. One mutation found "suggests the virus might be more inclined to bind to human cells rather than animal cells," Cheng said, but there's no evidence that it's becoming more infectious.

"If we started to see a lot more samples from Turkey with this mutation and saw the virus changing, we'd be more concerned," she said.

The Nature report cites a second mutation that also "signals adaptation to humans."

Flu viruses mutate all the time, Cheng said. "For us to assign public health significance to a genetic change we need to match it to what is happening epidemiologically -- how the virus is behaving -- and clinically -- if it's more or less virulent," Cheng said.

The avian flu first was detected in poultry flocks in Turkey in October. Then, on Jan. 5, the Turkish Ministry of Health reported that two teenagers, a brother and sister, had died from the disease, the first human cases outside East Asia.

Unlike in other countries, where cases were scattered geographically and the fatality rate was more than 50%, in Turkey, families have been affected, and there are more reports of people with mild symptoms. In addition to Turkey's 21 cases and four deaths, WHO has reported 145 cases and 78 deaths in Cambodia, China, Indonesia, Thailand and Vietnam.

"When this outbreak (in Turkey) was first reported, there was a lot of concern it was behaving differently," Cheng said.

That doesn't appear to be the case so far, Cheng said. "The team there told us that after two weeks of investigating, they haven't found substantial differences in the pattern we've seen in Southeast Asia."

She said the rapid increase of cases in a rural community in eastern Turkey is probably because of the practice of bringing poultry inside homes to protect them during cold weather, which would increase human exposure to infected chickens.

The mutations, which were detected by scientists at a lab in London, may "signify the virus is trying different things to see if it can more easily infect humans," Cheng said. "So far, we haven't seen that the virus has the ability to do this. But it's important that we continue monitoring."

The H5N1 strain first infected humans in 1997 in Hong Kong. It re-emerged in 2003, and efforts to stamp it out have failed. Health officials have seen no evidence yet that the virus can spread easily in humans.

"We would be concerned if we were seeing successive generations of spread of the virus" in Turkey, Cheng said. "We haven't so far. All these people had a very clear history of contact with diseased birds."

(c) Copyright 2005 USA TODAY, a division of Gannett Co. Inc.

Source: USA TODAY

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