A Guangzhou university's study of antibodies in Sars patients has indicated that people may come down with the disease without exhibiting clear symptoms, posing a problem for control. Li Gang, the deputy director of Sun Yat-sen University of Medical Science's infectious diseases department, said that they stumbled on this fact in a control group of people who are at high risk of contracting Sars. Blood serum samples drawn from more than 100 health-care workers at a hospital affiliated to the university showed that one of the staff had contracted Sars without knowing it because his symptoms were so mild. 'He had a fever of 37 degrees, muscle aches and general fatigue and rested for a day and recovered,' Professor Li said. 'This could pose a problem because we cannot detect the illness in these people and they are infectious.' None of the other health-care workers developed antibodies to the illness but about 200 samples drawn weekly from 20 patients treated at the hospital since February 2 found that all of them had antibodies. Immunoglobulin M (IgM) and Immunoglobulin G (IgG) started appearing in patients about 10 days after they contracted the illness. The IgM count peaked in 14 days and fell gradually over a two-month period before disappearing in three months in two-thirds of the patients, while IgG also appeared in 10 days but took two months to peak and was still at its peak three months after patients fell ill. Professor Li said the pattern of IgM and IgG development was similar to that of hepatitis A antibodies, which indicated that they, too, could be protective antibodies. 'IgG is the more important antibody, and in hepatitis B it can stay around in some patients for their entire lifetime,' he said. Professor Li said the university had applied for more funds to extend the study for up to two years to find out whether the IgG in Sars patients was also a protective antibody. 'We hope to increase our sample pool to 1,000,' he said.