THE outbreak of SARS early this year reminded Chinese that infectious diseases, which the public thought to be under control, still pose a threat to health and lives.

China is estimated to have 840,000 HIV carriers, including 80,000 AIDS patients, Gao Qiang, China's executive Deputy Minister of Health, announced recently. However, the official number of HIV/AIDS cases reported by health institutes to the Ministry of Health was only about 45,000.

That means there are nearly 800,000 unidentified HIV carriers and AIDS patients, many continuing their high-risk activities without taking precautions, according to Professor Jing Jun at Tsinghua University. He was speaking at an AIDS and SARS symposium held on the campus this week.

China still has a window of opportunity, that may disappear in two or three years, to control the deadly epidemic, said Ray Yip, an official from the Global AIDS Programme in China, supported by the US Centre for Disease Control and Prevention.

The information from the National Centre for Disease Control indicates that more than 60 per cent of HIV/AIDS patients in China were carrying the hepatitis C virus.

Compared with hepatitis A and B, hepatitis C, with similar transmission channels to HIV/AIDS, is less understood in China. In fact, the figure for infected patients stands at 37 million.

Meanwhile, medical experts have called for greater efforts to control and prevent the re-emergence of some "dead" infections, including TB and schistosomiasis, also known as snail fever.

Threatening thousands of people and livestock, the disease is still prevalent in 108 counties, most of which are economically backward. In China it can be found in the middle and lower reaches of the Yangtze River. Experts have estimated that more than 22 million people are at risk of infection from the disease if it returns virulently.

The present control programme cannot be efficiently carried out because of a shortage of money and technology.

Disease chart

The Chinese Centre for Disease Control and Prevention has released a chart depicting the development trend of China's infectious diseases over the past 10 years, based on the country's relevant research reports.

During the past decade, the occurrence and mortality rates of various infectious diseases in China have decreased in general, with ups and downs for different diseases.

There are obvious variations among different age groups and the most deadly diseases have changed. The highest mortality rates occur among the oldest and youngest groups. Presently the most threatening infectious diseases in China include hepatitis, tuberculosis, bacillary dysentery and tetanus neonatorum.

Statistics show that from 1999 to 2000, China's rate of infection from such diseases has dropped from 467.77 per 100,000 people to 295.37 per 100,000 people, and the mortality rate has dropped from 2.18 per 100,000 people to 0.93 per 100,000 people during the same period.

The two age groups - 1-10 and 20-30 years old are the most at risk of infection, while the age groups from 0-1 and from 65-75 had the highest mortality rate.

In terms of transmission channels, although the occurrence of respiratory tract infections and arborvirus diseases have decreased annually, hematogenic diseases and sexually transmitted infections have climbed year by year.

Before the year 2000, viral hepatitis and bacillery desentary had the highest occurrence, while in 2000 the occurrence of tuberculosis jumped to first place.