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. …