Investigators trying to establish how severe acute respiratory syndrome (Sars) infected more than 100 people in a single housing block in Kowloon are exploring the possibility that cockroaches carried the virus from floor to floor.

Authorities have been examining the waste system of the infected building at Amoy Gardens, and Leung Pak-yin, the deputy health director in Hong Kong, director, said that a clean-up operation, involving 100 government staff, was under way. “There is a chance that cockroaches may carry the virus,” he said.

Cockroaches are considered to be one of the most serious risks to public health. Species such as American, German and Oriental cockroaches can transfer filth and disease from rubbish to domestic environments, causing the contamination of food. Cockroaches are omnivorous, with a diet including food, hair, leather, wallpaper and faeces. Viruses are contracted by humans on being ingested with food that has been infected by cockroaches. However, a spokeswoman for the Hong Kong health authorities said that all kinds of insects, not only cockroaches, were being investigated, as well as rats.

So far Sars has infected 928 people in Hong Kong and has caused 25 deaths. Two more people died yesterday, both elderly men who were already suffering from other diseases. Of the 45 new cases yesterday, 18 were healthcare workers treating Sars victims at four different hospitals.

Samson Wong, a microbiologist from Hong Kong University, said that Sars might infect 80 per cent of the population within two years and eventually everyone could be infected. A Health Department spokeswoman said that the possibility could not be ruled out but declined further comment.

Evidence is mounting that a new strain of a virus linked to the common cold is the main cause of Sars. Scientists who examined 50 patients with Sars from five outbreak clusters said they believed it was a new member of the coronavirus family, best known as a cause of the common cold.

“We have provided evidence that a virus in the coronavirus family is the causal agent of Sars,” Malik Peiris, of the University of Hong Kong, said in a report published online by The Lancet. “However, it remains possible that other viruses act as opportunistic secondary invaders to enhance the disease progression.”

Dr Peiris and his colleagues identified the new type of coronavirus from two Sars patients and then looked for evidence of it in other patients and in healthy individuals. They found virus activity in 90 per cent of the patients, but not in any of the healthy control group.

In Canada, which reported its tenth Sars death yesterday, a surviving member of the family first infected by the disease complained that people had “treated us like monsters”. The woman, identified only as Ms Tse in her interview with The Globe and Mail, said that her family had been victimised repeatedly. Ms Tse’s 78-year-old mother, Kwan Sui-chu, became the first victim of Sars in Canada after travelling to Hong Kong on holiday and staying at the Metropole Hotel.

“People treat us like monsters,” Ms Tse said. “We are the victims. We were not staying at a pig farm. My parents went to a hotel on an American airline package.”

She said that a health clinic had refused to give her infant nephew his injections and a funeral home that cremated her brother, a Sars victim, had initially told the family to stay away before relenting.

The known global death toll from Sars now stands at 104.

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