BioEd Online

Cases of humans being infected with bird flu are rising in Asia, and there are worrying signs that the virus is mutating into a more transmissible form. But experts say bureaucratic delays will probably defeat attempts to stop a human pandemic in its tracks.

Klaus Stöhr, who coordinates the influenza programme of the World Health Organization (WHO), says there is only one option for extinguishing an emerging human pandemic: rapid identification of cases, and treatment of patients and all their contacts with the antiviral drug Tamiflu (oseltamivir phosphate). Modelling studies suggest this should work if action is taken quickly enough¹.

The models predict that there will be only a short window of opportunity in which to act: up to 30 days after a new case is detected. But the Vietnamese health ministry often takes two to four weeks to declare cases, according to the WHO.

"This leaves just a few days to intervene, making it very unlikely that we could stop a virus," says Stöhr. "Without fast reporting and detection of cases, the world is gambling away the small (and unproven) chance we have of stopping an emerging pandemic in its tracks."

On Thursday 5 May, WHO officials attended a meeting in Manila in the Philippines with government health representatives from Vietnam, Cambodia and Laos, to address the current flu situation.

Growing fears

Since the current outbreak of avian influenza began 18 months ago, the total number of human cases has risen to 89, and 52 of these people have died. The most recent case was announced by the Ministry of Health in Cambodia on 5 May.

To combat the spread of the disease, Vietnamese officials announced this week that they would vaccinate 600,000 poultry in Ho Chi Minh City against the flu.

At the same time, the European Union has recommended that its members should watch closely for signs of the flu virus in its poultry, including low-pathogenic forms. The move reflects growing fears that seemingly harmless versions of the virus may mutate into deadly forms.

In Asia, there are hints that the virus is indeed changing. "Incomplete evidence suggests that there may be a shift in the epidemiology of the disease," says Stöhr. "More clusters are being seen than last year, older people are now coming down with the diseases, and more cases are milder." Taken together, these characteristics could indicate that the virus is becoming less virulent and more infectious, he says, which could signal the start of a pandemic.

Hard to tell

But the WHO has so few data that it is "extremely difficult to assess the current situation", says Stöhr. It is hard to know how much we should worry, he adds. "It's as if you are driving along, and you hear a noise in your car engine, but you keep driving not knowing whether it is serious or not."

Stöhr says the WHO has offered assistance to Vietnam, but this hasn't been accepted fully. "The affected countries lack trust in the international agencies, including the WHO," says Robert Webster, director of the US Collaborating Center of the WHO that deals with the ecology of animal flu viruses. "There is a reluctance in these countries to give the agencies access."