H5N1 virus has not grown more dangerous, experts say

Jun 29, 2005 (CIDRAP News) – An international team of experts has concluded that the H5N1 avian influenza virus in Vietnam has not recently improved its ability to spread to or among humans, according to news reports published today.

The finding suggests that the immediate risk of a flu pandemic is lower than previously believed, according to an Agence France-Presse (AFP) report.

The report quotes Hans Troedsson, the World Health Organization's (WHO's) representative in Vietnam, as saying, "What was reported to the government is that, according to preliminary findings, they could not find any indication showing that the virus has actually extended its range in humans."

The specimens analyzed by the team of epidemiologists and virologists "did not show changes," Troedsson told AFP. He called the finding "very good news indeed."

"The most important thing is that we could rule out that there was an immediate, imminent pandemic," Troedsson said. "Since the virus is widely spread, the risk is still there but not as imminent as we initially might have suspected."

The story said the team concluded from "preliminary data" that the virus is not showing any increase in the efficiency of its transmission from birds to humans or from humans to humans.

In addition, the experts did not find evidence of previously undetected asymptomatic or mild human cases of H5N1 infection, Troedsson told AFP. The story did not specify how the team looked for such evidence.

Hitoshi Oshitani, leader of the team and regional advisor on communicable disease surveillance for the WHO, struck a cautious tone.

"We did not find any indications to show that the H5N1 virus is extending its range in humans, though clearly it retains that capability should it change," the Chinese news service Xinhua quoted him as saying.

The AFP story quoted Oshitani as saying, "While it's good news that we haven't documented a significant increase in the extent of transmission in humans, there is still no greater threat to winning the battle against avian influenza than complacency."

The team recommended that the Vietnamese government increase its surveillance of the virus in both animals and humans, Xinhua reported. In addition, the group advised the Vietnamese to share samples from future suspected cases with a WHO reference laboratory outside Vietnam for independent confirmation and quality assurance.

The team included experts from Australia, Canada, Hong Kong, Japan, the United Kingdom, and the United States, Xinhua reported. They left Vietnam yesterday after spending a week there.

In May, a panel of experts convened by the WHO in Manila had reported that changing patterns of cases in northern Vietnam suggested that the H5N1 virus might be becoming more infectious for humans. The panel had cited an increase in case clusters, an increase in patients' average age, and a decrease in the case-fatality rate.

The panel also had said genetic studies indicated that H5N1 viruses were becoming more antigenically diverse.

In today's AFP report, Troedsson said the experts who just left Vietnam were able to do "more advanced testing" than had been done at the time of the Manila meeting. The story didn't say what kinds of tests were done.

Elsewhere, Singapore said it has begun preparing for a flu pandemic by stockpiling an antiviral drug and taking steps to secure a vaccine, according to another AFP report today.

The country's health ministry said it has begun buying oseltamivir (Tamiflu), which is used to prevent and treat flu. In addition, the story said, the ministry is exploring possible collaborations with vaccine manufacturers to produce H5N1 vaccines and ensure access to vaccines when they become available.

According to the WHO, 108 people have contracted H5N1 infections and 54 have died since the current series of outbreaks began in late 2003.

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