办事指南

Kentucky delivers TB warning

点击量:   时间:2017-12-05 05:01:07

By Jonathan Knight A STRAIN of tuberculosis that is easily spread through casual contact has been identified in rural Kentucky. Researchers at the US Centers for Disease Control and Prevention (CDC) in Atlanta warn that similar strains could turn up elsewhere, and advise doctors to be vigilant. Although the TB bacterium can spread through the air, transmission is normally infrequent. So Sarah Valway and her colleagues were intrigued by an outbreak in a small southern Kentucky village, in which 21 people contracted TB between 1994 and 1996. To find out how many other people had come into contact with TB without becoming ill, the researchers screened friends and relatives of three of the patients for the presence of TB bacteria, using a standard skin test for antibodies. In The New England Journal of Medicine (vol 338, p 533) they report that 72 per cent of these contacts tested positive—several times more than would be expected. Valway then infected mice with the new strain and found 1000 times more bacteria in their lungs after 20 days than in mice infected with a standard laboratory strain. She believes this accounts for the greater rate of transmission: “A bit faster growth gives a whole lot more bacteria.” A few strains of TB are now resistant to drug treatment. If one of these were as easily transmitted as the Kentucky strain, it could be devastating. “That is what we were terrified of,” says Valway. Since TB bacteria tend not to exchange genes, the mingling of high-transmission strains with drug resistant ones is unlikely to produce a superbug. But such a deadly strain might appear spontaneously via a random mutation. “This report ups the ante on the pace at which these cases need to be identified and treated,” says Peter Small,