Experts Worried by Animal Virus That Killed Boy

The World Health Organization (WHO) is worried that mutating viruses able to leap species could cause another world flu pandemic, such as the ones that occurred in 1968 and 1957 and killed thousands of people.

So far, local health and agricultural officials have established an outbreak of fowl flu on chicken farms in Hong Kong's northern New Territories and in southern China. "It seems the (dead) boy was in contact with chicken farms where there has been an outbreak of this virus," said Dr. Daniel Lavenchy, head of the WHO's influenza programme in Geneva, Switzerland.

Researchers at the U.S. Center for Disease Control and Prevention in Atlanta say that although the Hong Kong case was an isolated one, it could lead to a sudden epidemic if precautions are not taken.

The virulent virus, which wiped out thousands of chickens within days in farms in Hong Kong and southern China, was identified by international scientists as a new subtype not previously seen in humans and was dubbed H5N1. Dutch scientists at the National Influenza Centre of the Netherlands believe it to be similar to the two viruses that caused the two previous flu pandemics.

Scientists now believe the fowl flu virus it directly infected the boy. The confirmation that the virus jumped from fowl to boy has raised new concerns about the intensive manual farming of pigs together with ducks or chickens -- particularly in areas which are also densely populated with humans such as southern China and Hong Kong.

Such close farming of livestock can lead to bird viruses being passed on to swine, which in turn may pass the mutated virus to humans.

In the 1960s, virus-carrying ducks from southern China were found as far afield as Canada, leading to the hypothesis that the killer flu of 1968 was caused by a virus which jumped from fowl to humans and spread to North America and Europe as well as much of Asia as the ducks migrated across long distances.

Virology experts believe the flu virus breeds in the intestine of ducks. Flooded rice fields are a "fecal soup" of the duck virus, they say. The disease is believed to be passed on to pigs given the intense and close farming of pigs and ducks, and then on to people.

"It is in this part of the world that man and animal live in very close association, perhaps more closely than anywhere else in the world on a big scale," said Tim Shortridge, professor of microbiology at Hong Kong University.

A major research program in the West to find the origins of the 1968 flu pandemic concentrated on duck farms in Yunnan province, China. "In the area of southern China, including Hong Kong, there's a tendency to have more new viruses occurring, for reasons we don't know," said Lavenchy.

Research on the new virus will help develop a vaccine. It takes between six and nine months for a virus to emerge and be transmitted, depending on climatic conditions. A spring virus in Hong Kong may be transmitted to North America or Europe by the autumn.

But unlike the 1950s and 1960s virus, H5N1 appears to be a weak virus in terms of transmissibility.

In the New Territories and in southern China "the disease burnt itself out and has not been seen again in chickens since the spring," said Barry Bousfield, a veterinarian with Hong Kong's Agriculture and Fisheries department, which has been monitoring all chickens crossing the border from China for signs of infection.

Likewise, tests on chicken farmers, veterinarians, the dead boy's family and playmates failed to turn up other cases of the strain of flu virus.

This means the virulence of the new strain is still unknown. But the mutation between the boy's virus sample and the chicken's sample, called "antigenic shift" in medical jargon, will indicate whether H5N1 will remain an oddity or have the potential to lead to another flu pandemic. Tests are being conducted in Atlanta to ascertain this.

"A shift is what happened in 1968," said one scientist linked to the case. "When there is a sudden change in the virus most people don't have immunity."

Meanwhile, the WHO will begin a major study of pig farms in southern China to better understand the mode of transmission of animal viruses to humans. Some experts believe pigs are the main transmitter of viruses to human beings. "The idea is to study the virus which affects the pigs and how it is transferred to human beings," Lavenchy said.