The severe drought ravaging southwest China, home to an ingredient in the anti-flu drug Tamiflu, may prompt Roche, Tamiflu's biggest producer, to use substitute ingredients.

Southwest China produces 85 percent of the world's Star Anise, an ingredient of Tamiflu, and the region's production may be "substantially reduced" as a result of the drought, said Li Changxin of zyctd.com, China's biggest traditional medicine trading website.

Two thirds of the Star Anise used by Tamiflu's biggest producer, F.Hoffmann-La Roche Ltd., comes from China, said Lu Shunzhong from the Forestry Research Institute of south China's Guangxi Zhuang Autonomous Region.

But Roche spokesman Cao Yong told Xinhua he is "not aware of any possible effect on Tamiflu's production posed by the drought."

Star Anise is the best source of shikimic acid, an indispensable part of Tamiflu, which is used against the A/H1N1 flu, said Li Yi, secretary general of Guangxi's Flavors and Fragrances Industry Association.

While it is true a major event like the drought could have a ripple effect, Star Anise can be substituted, and so Tamiflu's production will not be greatly affected, Cao said.

Guangxi produces 80,000 tonnes of the plant annually, about 85 percent of total world production, according to Guangxi Forestry Department statistics.

"Up to 30 percent of the Star Anise plants in Guangxi are withering," said Yang Wende, head of Guangxi's Star Anise Association.

In Yunnan province, the second largest producing region, over 7,000 Mu (466.7 hectares) will see no yield at all while 50,000 Mu of Star Anise crops are withering, said a Yunnan forestry official surnamed Yang.

Star Anise demand is expected to outweigh supply in Guangxi, and its price has already tripled since early 2009, Li said.

The drought has been ravaging southwest China for months, affecting 61.3 million residents and 5 million hectares of crops in Guizhou, Yunnan, Sichuan, Chongqing, and Guangxi, the Ministry of Civil Affairs said Wednesday.

Demand for Tamiflu may rise sharply if the A/H1N1 flu spreads. Flu cases have been reported in 213 countries and regions and had killed at least 16,455 at the end of Feb. 2010.

The World Health Organization's emergency committee of experts said on Feb. 23 that it is still too early to say the A/H1N1 flu pandemic has peaked.

The Chinese Center for Disease Control and Prevention warned the A/H1N1 flu is "very likely" to break out in summer in southern China.

China's export of Star Anise accounts for over 80 percent of the world's total, with Guangxi exporting 1,714 tonnes in 2009, up 46.5 percent from 2008.

Roche is a Swiss global health care company with headquarters in Basel, Switzerland, and offices around the world.