Investigations are underway after an unconfirmed illness killed 17 farm workers and left at least 12 in a critical condition in hospital in southwest China's Sichuan Province in the past few weeks.

Zeng Huajin, a senior official with the provincial health department, said it was "probably" caused by Streptococcus suis, a bacteria usually spread among pigs.

"I can assure you that the disease is absolutely not SARS (severe acute respiratory syndrome), anthrax or bird flu," the official said last night.

"We still need further research to confirm whether it was caused by Streptococcus suis," he added.

An initial 20 farm workers who handled sick or dead pigs and sheep in 12 towns and 15 villages in Jianyang City and Ziyang City's Yanjiang District suffered from high fever, nausea, vomiting and hemorrhaging.

But more cases were reported as health workers began to search villages for the sick.

"By noon on Saturday, 58 people suspected of having the disease had been reported in Ziyang and (neighboring) Neijiang," according to a statement last night from the province's health department.

"Two of them have been discharged from hospital while 27 are recovering," the statement said, adding that the patients were from 49 villages of 23 townships and not related to each other.

Zeng said Streptococcus suis could not spread among humans, and normally only those with a weak immune system became ill.

The health and agriculture ministries sent a special team to Sichuan last week to assist in the investigation, treatment and control of the outbreak, but were not available for comment yesterday.

"This is a good job of disease surveillance, and shows China has vastly improved its system since the SARS period in 2003," WHO spokesperson Bob Dietz was quoted by Bloomberg as saying.

A physician at Ziyang No.1 People's Hospital said yesterday that people could quickly become ill and doctors were busy carrying out emergency treatment.

All patients were reportedly being treated at three hospitals in Ziyang.

Yesterday, Hong Kong put out an alert relating to the disease, but Secretary for Health, Welfare and Food York Chow said frozen pork from Sichuan is safe to eat.

He confirmed that no live pigs are imported from the province into the territory and that frozen pork imports come via designated companies with permits from Hong Kong health authorities.

According to the UK Health Protection Agency, Streptococcus suis is endemic in most pig-rearing countries, but only about 150 cases of human infection have been reported until now and they are thought to take place mainly via cuts or abrasions when handling infected carcasses.

(China Daily July 25, 2005)