With the increase of schistosomiasis cases reported in recent years, a Chinese health expert warned here Sunday that China faces grim challenges in curbing schistosomiasis and there is a possibility for the diseaseto spread further if no effective measures were taken.

Zhou Xiaonong, a researcher at a Shanghai-based national institute of verminosis, said that to find a way to lower the big number of schistosomiasis patients is one of the challenges China faces.

China launched the campaign against schistosomiasis since early1950s and successfully limited the disease to only seven provinces.The estimated number of the country's schistosomiasis patients has been reduced from 11.6 million to 843,007 during the past five decades, down 92.74 percent.

"However, the estimated number of schistosomiasis patients on the Chinese mainland has remained at 800,000 in recent five years and there was no sign of declining," Zhou said.

In 2003, China reported 1114 acute schistosome infected patients, indicating a 22 percent increase on a year-on-year basis.

Schistosomiasis is a kind of infectious verminosis, which is caused by infestation with schistosomes, widespread in rural areas of Africa, Asia, and Latin America through contaminated water. The disease is characterized by infection and gradual destruction of the tissues of kidney, liver and other organs. Oncomelania is the carrier of schistosomes.

"Recent five years have witnessed an expanding of oncomelania areas," Zhou said. In 2003, the areas where oncomelania were discovered expanded 268 million square meters compared with the figure in 2002 and among the 20 surveillance areas nationwide, 17 reported oncomelania.

Zhou said the spread of oncomelania led to the rebound of the disease in certain areas where the transmission of schistosomiasis had already been put under control or cut down.

In the mid-1990s, schistosomiasis patients were reported at some places which traditionally were not schistosomiasis-infected areas and in recent five years, 38 counties and cities where the transmission of schistosomiasis had been contained or intercepted reported obvious increase of cases, Zhou said.

In addition, Zhou said the spread of schistosomiasis from ruralto urban areas is another dangerous phenomenon. Statistics showed that during the past five years, some middle- or small-sized cities reported infectious on comelania and schistosomiasis patients. Some places where schistosomiasis had been eradicated reported imported acute or chronical cases.

Zhou said natural factors like frequent floods at the Yangtze River reaches in recent years have for sure caused the spread of oncomelania, but there are also "human factors" like the building of some water projects, lack of financial support and slow progress in scientific researches.

Zhou said he was glad to see that the rebound of schistosomiasis has aroused serious concern from China's central government, which treated health issues as one of its priorities after last year's SARS outbreak.

In February this year, the State Council set up a working groupon schistosomiasis with Vice Premier Wu Yi as the group leader. "It's foreseeable that the government will exert much more efforts in the control of this disease," Zhou said.