While not uncommon in pigs, Streptococcus suis is seldom seen in people and never dozens of cases all at once — raising bigger questions about whether the germ has mixed with some other bacterium or virus.

“Something is different,” Marcelo Gottschalk, one of the world's leading experts on the disease, said Wednesday.

“We are worried and we wonder what's happening. We would like to have the strain to identify.”

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Dr. Gottschalk works in the world's only reference laboratory for Streptococcus suis at the University of Montreal in Canada and says no one in China has contacted him for help since the outbreak was reported last month.

So few people have studied this disease, he's unsure how the Chinese have been able to identify it and what type of vaccine they plan to use since immunizations typically are not effective.

Chinese state media have reported that enough vaccine for 350,000 pigs has already been sent to Sichuan province from a company in southern Guangdong province and that enough doses for 10 million swine will be shipped later.

Dr. Gottschalk said Streptococcus suis usually takes a while to develop in people and often causes meningitis followed by partial or permanent hearing loss. Most people also survive after being treated with antibiotics and cases are typically few and far between — Thailand, for example, usually has less than 20 known cases a year, he said.

China has reported more than 200 confirmed or suspected human cases since June.

The infected farmers who handled or butchered sick pigs have experienced nausea, fever, vomiting and bleeding under the skin.

The World Health Organization and the UN Food and Agriculture Organization have questioned whether Streptococcus suis could possibly have combined with some other disease or bacteria in China.

One case has also been reported in Guangdong province, hundreds of kilometres southeast of Sichuan. Hong Kong has reported two infections since the latest outbreak, but Chinese health officials have not announced whether those are connected to the Sichuan cases.

“Why is it behaving differently all of a sudden?” said Juan Lubroth, an animal health official at FAO in Rome. “One explanation is you have additional problems and it's not just Streptococcus suis that's causing it.”

Thomas Alexander, retired deputy director of the University of Cambridge's School of Veterinary Medicine, was a pioneer in studying this particular strep germ.

He said the bacteria is commonly found in the tonsils of healthy swine in different parts of the world. However, it sometimes becomes pathogenic when too many pigs are crammed together in unsanitary conditions.

“In my experience, it's much more chronic. They're describing death within 24 hours,” he said by telephone from England. “What they're describing doesn't fit the picture.”

The disease is typically spread from pigs to people through cuts or wounds on the hands. Pork that has been thoroughly cooked is not a problem, but eating undercooked or raw meat can infect humans.

Asia has been particularly aware of cross-species infection since 2003 when it fought SARS, which is believed to have first jumped from animals to people in southern China; it eventually killed nearly 800 people worldwide. The region is also currently battling bird flu in which poultry has infected humans, killing at least 60 people since 2003.

China was accused of withholding information about SARS, and WHO has recently said health officials are not sharing enough information about bird flu.

Based on his limited information, Dr. Gottschalk said he's not overly concerned about the pig disease spreading across borders since bacterial diseases tend to change more slowly than viruses like flu. There have been no cases of Streptococcus suis spreading from person to person.

He would, however, like the Chinese to send samples so he can try to identify the strain.

“It's extremely difficult for us get the real information for Chinese agriculture,” he said. “I'm not really sure if they have all the background necessary to study this bacteria or infection. Few labs in the world are capable of studying this.”

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