After two students contract the disease, health officials check 85 pupils and staff About 85 students and teachers at a secondary school in Wang Tau Hom are undergoing checks for tuberculosis after two students contracted the disease. The Department of Health confirmed yesterday that 35 students and 15 teachers at the PHC Wing Kwong College who had direct contact with the two patients had been given the all-clear after X-rays on Tuesday and Wednesday. Another 35 students will have a checkup on Monday. A 14-year-old boy and a 19-year-old girl were confirmed to have tuberculosis on September 23 and 25, respectively. The department visited the victims' families in an attempt to trace the source of the disease. Family members were found to be free of the disease after X-ray checks. The boy was admitted to hospital on September 21. He has been discharged and returned to school on October 3, according to a spokesman for the school. The girl has been on sick leave since September 24 and has not returned to school. School principal Kwok Man-kwan said the school had stepped up cleaning and disinfection on campus. He said it was not necessary to close the school. The school, which was opened in 1973, has 920 students and 55 staff. Tuberculosis is a notifiable disease in Hong Kong and a total of 6,608 cases were recorded last year, with a death rate of 4 per cent. University of Hong Kong community medicine professor Gabriel Leung said the TB vaccine provided only about 60 per cent protection. He said it was important for people to maintain good personal hygiene. Dr Leung said 30 per cent of people who were directly exposed to tuberculosis patients for a long time would be infected, but only 1.5 per cent would develop the disease. Tuberculosis is caused by the bacteria mycobacterium tuberculosis. It usually affects the lungs, but can also affect the lymph nodes, kidneys, bones and joints. Symptoms of pulmonary TB include low fever, night sweats, fatigue, weight loss, a persistent cough and blood in sputum. Some people may not have obvious symptoms. Tuberculosis is spread through the air. When a person with infective pulmonary tuberculosis coughs or sneezes, the bacteria becomes airborne and a person can be infected through inhaling the air. Symptoms may occur as early as several weeks after infection, or after many years, but an infected person has the greatest risk of developing TB within the first two years after infection. The department warned that people with tuberculosis should seek medical treatment as soon as possible. They are prescribed drug therapy for at least six months.