Summer flooding could cause a surge of cases of the Sars virus in China, the World Health Organization has warned.
China is facing a huge challenge fighting the virus
The Sars virus does not appear to be spread by water, but it can survive for days in human waste, which might be spread by overflowing sewage, the WHO said.
Flooding is already creating havoc in China. More than 70 people were reported on Wednesday to have died in torrential rains in the south of the country.
And Sars is continuing to take its toll. Beijing, the world's worst-hit city, has more than 27,700 people under quarantine, mostly in hospitals.
Neighbouring Taiwan is also continuing to struggle with the virus. The WHO has extended its travel ban to the entire country, rather than just the capital, Taipei, as the Sars virus continued to spread.
The WHO admitted on Wednesday that it had responded too slowly to Sars.
Mark Salter, the specialist from the World Health Organization who is charged with stopping the disease spreading said the WHO had not always been "as responsive and as quick as some people might like" in the early stages of the disease.
The flu-like Severe Acute Respiratory Syndrome has killed about 662 people worldwide and infected more than 7,800 people - mostly in Asia - since it emerged in southern China in November
Known death tolls:
Mainland China: 348
Hong Kong: 298
Source: WHO/local authorities
Every year, areas throughout southern, central and north-eastern China are hit by deadly flooding. Dozens of deaths have been reported this week in floods and landslides in the southern provinces of Hunan, Fujian and Guangdong.
Thousands of rural homes face being flooded by water laced with sewage that can also contaminate drinking water.
"We see this as a potential threat, something to beware of," said Bob Dietz, a WHO spokesman in Beijing. "Sars could rear up again."
The WHO fears poor health facilities in rural China, already strained by Sars, will come under further pressure as they deal with other illnesses and injuries caused by flooding.
But Mr Dietz said there was no way of preventing the problem.
"You can't stop flooding and there's nothing that can be done to improve sewage systems at such a short order," he said.
The WHO has also been looking into the possible impact of Sars on people suffering from HIV/Aids.
A team of WHO experts have returned to Beijing from a trip to Henan province, where thousands of villagers were injected with HIV through illegal blood donations.
They have yet to publish their findings.
In neighbouring Taiwan, which the WHO has described as the "most rapidly growing outbreak at present", with 52 people dead, no new fatalities were reported on Wednesday, but there were 35 new infections.
The WHO said on Wednesday that all non-essential travel to the island should be postponed.
The majority of Sars cases in Taiwan have originated in hospitals and more than 150 doctors and nurses have left their jobs in protest at the lack of safeguards to prevent staff catching the virus.
In Hong Kong, officials said two more people had died in the territory, bringing the death toll to 255.
In other developments:
- The Philippines is declared Sars-free after 20 days with no new cases detected. Two people died during the outbreak there.
- The Malaysia Open badminton championship scheduled for 1-6 July is postponed over Sars fears
- Singapore plans to launch a state-run TV channel on Wednesday, dedicated to news and information on the virus
- Japan's health ministry calls an emergency meeting after admitting it failed to act for almost a day on a report that a Taiwanese doctor visiting Japan earlier this month may have been infected with Sars