Hong Kong virus spreads worldwide

Cases of severe acute respiratory syndrome, an atypical pneumonia that emerged earlier this month in Hong Kong and Vietnam, have now been reported in 14 countries.

By 24 March, according to the World Health Organization, there were 456 suspected and probable cases, more than triple the number from a week earlier, and 17 deaths as a result of the disease. “It's not stopping yet,” said Mr Peter Cordingley, the WHO's spokesman in Manila.

The total includes 37 suspected and probable cases in 18 US states, although the latest available figures from the US Centres for Disease Control and Prevention (CDC) put the total at 39.

“This is the figure that stood out for us,” said Mr Cordingley. “It's not that we didn't expect [further US cases], but this is rather larger than we expected. All the cases, with the exception of two healthcare workers, were infected overseas. How they became infected is still not known but it's through a variety of routes — Hong Kong, Singapore, and Vietnam,” Mr Cordingley added.

However, the US figures may turn out to be artificially high as the authorities are including those with symptoms that fall well short of pneumonia in the hope of catching all cases.

WHO has set up a collaborative multicentre research project to coordinate the worldwide effort to establish the cause of the outbreak. On 19 March researchers at the Chinese University of Hong Kong announced that they had isolated the mystery virus and identified it as a member of the paramyxovirus family, a large family that includes the viruses that cause measles, mumps, and various respiratory infections. These findings concurred with those of scientists in Canada and Germany, who also found evidence of a paramyxovirus in cases there.

However, virologists at the University of Hong Kong said on 23 March that the cause is a new virus, without clarifying whether or not it is in fact a member of the paramyxovirus family. Researchers in the United States cultured a new corona-virus in the same family as viruses that cause colds and upper respiratory tract infections and this is the CDC's leading hypothesis for the cause of the infection. “The WHO is still being very cautious on the cause of the outbreak,” Mr Cordingley said.

Scientists in Hong Kong have developed a reliable diagnostic test for the infection and doctors have been treating cases of the infection with a combination of the antiviral drug ribavirin and steroids. “Over 100 individuals are on treatment and 85% have shown improvements in their condition, so this is encouraging,” said Dr Yeoh Eng-kiong, Hong Kong's secretary for health, welfare, and food.

The index patient who carried the infection to Hong Kong was identified as a semiretired doctor from Guangdong province who was ill during his stay at a Hong Kong hotel and later died in hospital there. He infected the index case for the main outbreak at Hong Kong's Prince of Wales Hospital. Cases in Canada, Singapore, the United States, and Vietnam, however, have all been linked to him through stays by people at the same time on the same floor of the Metropole Hotel.

WHO has said that the outbreak most likely originated in Guangdong, and it has urged mainland officials to provide more data on the outbreak there. Although an outbreak of atypical pneumonia in Guangdong province began in November 2002, the Chinese authorities informed WHO only on 11 February that the outbreak had occurred and never officially reported to WHO that it had killed five and infected 305 people.

There is some scepticism about claims of the provincial authorities that the outbreak in Guangdong is under control. A WHO team is in China to help the Ministry of Health investigate the source of the syndrome.

Hong Kong remains the centre of the outbreak, and by 4 pm on 24 March there were a total of 260 confirmed cases of atypical pneumonia, up from 83 on 17 March, including 38 people in intensive care and 10 deaths. (See p 669.)