China's pig disease baffles health experts

Human-to-human transmission mooted

A pig-borne disease that has killed 36 people and infected 198 in China may be spreading from human to human, according to some scientists, while others suggest an entirely different disease is to blame.

The Chinese government, which has just delivered the first shipment of pig-vaccines to the affected area, says no evidence of human-to-human transmission has been found, and the spread of the disease is now under control.

But experts counter the denial, pointing out that transmission from pig to human is actually quite difficult, and that the high numbers of infected people suggest the disease is spreading from person to person.

"The organism is carried on the pig’s tonsils and is spread pig-to-pig through nose rubbing or coughing. But it’s only found in small concentration on the pigs’ tonsils, so it’s difficult for a human to catch it that way," Jill Thompson from the UK’s Veterinary Investigation Centre in Edinburgh told New Scientist.

Authorities in China became aware of the disease in late June, but only made an official announcement a month later on 25 July. Comparisons are already being made with the way authorities handled the SARS and Bird Flu outbreaks.

According to New Scientist, the World Health Organisation professes to be baffled by the outbreak, because the bacteria concerned - Streptococcus suis type II - has never affected so many people at once. It also appears to be a particularly virulent strain - mortality rates are usually below 10 per cent - and those infected are exhibiting unusual symptoms.

Samson Wong, a Hong Kong University microbiologist, says that the presentation is so atypical, it might even be another disease altogether. He notes that many patients were bleeding under the skin, a rare symptom of the infection, and that few cases of deafness, a more common symptom, have been reported. Other scientists suggest a virus might be responsible for the outbreak.

Jill Thompson goes on: "It is so rare for humans to become infected; most farm workers develop some immunity from the endemic disease. What might have happened is that the bacteria have acquired virulence factors from another organism - a bacterium or virus that might be harmless - and the combined virulence factors have turned it into a superbug, which could be transmitted human-to-human through coughing." ®

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