Scientists will test the blood of relatives of patients to check for virus antibodies Hong Kong scientists will investigate if family members and other close contacts of Sars patients have been exposed to the virus to find out how the disease spreads in the community. The serological study, jointly conducted by the Department of Health and the University of Hong Kong's medical faculty, will invite more than 2,500 close contacts of Hong Kong Sars patients to take a blood test to check if they carry antibodies of the coronavirus. Lam Tai-hing, a professor in the university's Department of Community Medicine, said yesterday that the study, the first of its kind globally, will provide useful information in preparing for the next outbreak. 'From the public health point of view, the study findings will tell us how many patients got infected but have not shown symptoms. We also want to know why some family members of Sars patients, despite their very close contact, did not contract the virus,' Professor Lam said. Each person interviewed will be invited to give blood for the tests at the Department of Health's regional offices or elderly health service. Department nurses will start interviews on Monday. The research team expects the results to be available by the end of this year. The Chinese University said last month that it would test the blood of about 10,000 Hong Kong people to find out how many have been exposed to Sars. The Guangdong Centres of Diseases Control and Prevention in Guangzhou is also planning a study to investigate the prevalence of Sars antibodies in its general population after 13 per cent of wild animal traders were found to have been exposed to the disease. Lau Yu-lung, the University of Hong Kong's chair professor of paediatrics and adolescent medicine, said his team would conduct similar antibody tests on 600 to 800 children to find out how Sars spread among the young. The children would come from two districts - Kowloon Bay, including the Amoy Gardens estate where 42 people died, and Southern district on Hong Kong island, which was barely affected by the disease. Meanwhile, the head of the university's Genome Research Centre, Paul Tam Kwong-hang, said its laboratories would be responsible for conducting DNA sequencing for the virus. Research would also be done to find out if any genetic factors made a particular group of people more vulnerable to infection, Professor Tam said. During the Sars outbreak, the centre was the third facility to complete mapping the genetic code of the coronavirus, after the Genome Sciences Centre of the British Columbia Cancer Agency in Canada and the Centres for Diseases Control and Prevention in America.