To ward off the new SARS pneumonia virus, ethnic Chinese in San Francisco are flocking to their traditional herbal medicine shops.

Herbal apothecaries in San Francisco's Chinatown say they are doing a roaring trade in dried herbs, roots and other ingredients for a potion that many believe fortify the body against virulent illness.

"There are many ways to protect against SARS," York So of the Wan Hua herbal medicine shop said.

"But this is the best" of the potions aimed at thwarting Severe Acute Respiratory Syndrome, he said, waving a list of some 10 esoteric herbs he packages to be boiled and drunk to steel the body against the virus which has killed 170 people and infected more than 3,500 worldwide.

The lethal virus has hit hardest in southern China and Hong Kong, the birthplace of many of San Francisco's immigrant Chinese and waves of fear have spread to the US West Coast.

Since it was first recognized in March, many ethnic Chinese here have feared that SARS could further spread in California where 42 suspected or probable cases have already been reported, making it the hardest-hit US state.

With no cure yet developed, residents of the many US Chinese communities, including San Francisco and Los Angeles, have snatched up all of surgical face masks and turned to traditional medicine shops for preventive potions.

One old woman in Los Angeles's Chinese quarter was selling packets of what appeared to be a plant root saying they can help ward off SARS, but quickly withdrew the product when approached by reporters.

But in San Francisco, the recipe So uses is proving most popular among Chinese residents anxious about SARS.

It is a mix of natural ingredients developed by China's respected Guangdong Institute of Traditional Chinese Medicine and popularized over local California Chinese-language television and radio.

The concoction includes esoteric herbs like black figwort root, woad root, prunella spike and Japanese honeysuckle as well as chrysanthemum flowers.

So has his customers boil it into a thick tea and drink it three days straight. It cleanses the body of poisons and will reduce fever and sore throat, he says.

The same recipe is posted on the wall behind the counter at Yu's Chinese Herbs, along with a Chinese newspaper article extolling its effectiveness in warding off SARS and other fevers.

The pharmacy's owner Yu Li says demand for the mixture has increased significantly since the SARS outbreak. He sells the three-day treatment for nine dollars.

So stresses that the herbal blend is only a preventive. "So far, we haven't had SARS here yet. This mixture is the best for protecting you."

"Of course," he adds, "if someone is really sick, we tell them to see a Western doctor," he adds.

SARS, is an atypical and deadly strain of pneumonia caused by a coronavirus which appears to have originated in Asia.

From ChinaDaily.com.cn