Sars experts study animal link

A new theory says rats were to blame for the Hong Kong outbreak

A team of international experts has arrived in southern China to study links between animals and the deadly pneumonia-like Sars virus, which killed more than 800 people worldwide earlier this year.

The experts, including World Health Organisation scientists, are visiting livestock farms, markets and restaurants in Guangdong Province, where the disease is believed to have started.

People in the province are known for their taste for eating exotic animals.

In Hong Kong, an epidemiologist has put forward a new theory to explain the rapid spread of the virus in the territory.

Writing in the Lancet science magazine, Stephen Ng from Columbia University School of Public Health in the US said rats living in pipes and light wells quickly spread Sars among the residents of the Amoy Gardens high-rise housing estate, after one of the rodents was infected by a human.

I suggest the epidemic could have been started by a rat going into an apartment visited by the patient and being infected by contaminated material, such as used tissue paper, leftover food, or excreta Epidemiologist Stephen Ng

A total of 321 people living in 15 blocks in the territory fell sick with Sars from late march to mid-April.

Mr Ng's theory challenges a government inquiry in Hong Kong which found that the initial source of the Sars outbreak was a man who had spent two nights at his brother's home in the estate.

The inquiry said droplets from his contaminated faeces then travelled through interconnected sewage pipes into faulty bathroom pipes, and infected others that way.

But Mr Ng said it would have been impossible for one patient to infect so many in such a short amount of time.

Instead, he is blaming local black rats - called roof rats in Hong Kong - which have adapted to high-rise living to such an extent that they use clothes lines to scuttle from building to building.

Rat Number 1, Mr Ng wrote, could have picked up the virus from infected material from the established first patient, before passing it on to other rats.

They, in their turn, would have carried Sars to other households, depositing the virus in their droppings or saliva.

Mr Ng says the theory needs further exploration, but maintains that it is still a strong possibility.

No guarantees

The BBC's Francis Marcus in Shanghai says that for most people in China Sars is now a memory, not yet distant, but put aside with relief.

There have been reports of the corona virus which causes Sars being found in animals such as the civet cat.

But after months of investigations, experts are still not sure where the disease originated and they fear it could return.

The fact that the group of international experts has begun a mission to probe the origins of the disease underlines how little we know about it, our correspondent says.

The scientists will try to establish ways in which Sars may be linked to animal populations despite numerous studies already showing its presence in various species.