This level of infection makes TB among the homeless nearly 200 times more prevalent than in the general population. Last year there were 6,000 cases, an 18 per cent increase since 1987. A spokesman for the World Health Organisation (WHO) said the London figures were 'startlingly high'.
Crisis, a charity for the homeless, said yesterday that the Department of Health and the London Housing Foundation had funded a pounds 15,000 emergency screening programme for people in London's winter shelters. Health workers, who aim to screen more than 350 shelter seekers and workers, have under three weeks to reach them before the cold-weather shelters close at the end of the month.
At the same time, the Communicable Disease Surveillance Centre of the Public Health Laboratory Service (PHLS) is stepping up its monitoring of drug-resistant TB. During 1993 all reported TB cases were analysed and results are expected later this year.
Doctors have been alerted to the severity of the problem from the results of screening 250 men and women in shelters over Christmas. They found four active cases, of whom two men were in a highly infectious phase. The chest X-rays revealed another four 'very likely cases' but these men did not attend hospitals for their follow-up check so their disease could not be confirmed. In 17 cases there was evidence of old, inactive TB but poor health and living conditions could activate the condition.
'Such a high incidence of a disease that many people think has disappeared reflects the appalling conditions in which many homeless people have to live,' Mark Scothern, director of Crisis, said. Dr Ken Citron, consultant physician at the Royal Brompton National Heart and Lung Hospital, said: 'We have always known that the homeless are very vulnerable. TB is a disease which you see when nutrition is poor, where social conditions are bad, with some people sleeping rough. It is also true that homeless people do not seek medical help until they are seriously ill, therefore most of the cases we pick up are likely to be advanced and infectious.'
One of the problems is that it is hard to persuade homeless people to complete the treatment, a six- month course of antibiotics that will cure TB. Taking only part of the course encourages drug-resistant strains of TB to develop and spread.
Dr Deepti Kumar, medical statistician of the PHLS surveillance centre, who analysed the data from the Christmas screening, said: 'There is a danger of it becoming epidemic in hostel conditions. Hostels with poor ventilation create conditions which are absolutely right for transmitting the disease, as we have seen in New York.'
Dr John Watson, consultant epidemiologist in respiratory diseases at the PHLS, said the increase could be because of an increase in cases in the elderly, in people with HIV, in refugees and because greater interest has increased the number of notifications.
A spokesman for the Department of Health said that the results of Crisis's Christmas and current TB surveys would 'give us a clearer picture of the levels of TB in any homeless population and enable us to make recommendations for the longer term and nationally'.
In inner-city New York, WHO population figures show highest rates among the black population of 0.11 per cent. Across Africa, rates for whole populations for all types of TB are between of 0.1 per cent to 0.2 per cent.
When TB recording began in Britain in 1913, there were 117,000 notifications. This had fallen to 20,000 by the 1960s and continued to fall, levelling off in the 1980s and then starting the slight rise again about five years ago.
The TB bacillus was discovered by Robert Koch in 1882 and antibiotics became available during the late 1940s. However, improved living standards with better food and less overcrowding were most important in bringing about the decline of TB in Britain.