VOA慢速英语 2008 1027a（在线收听）
An estimated one-third of all people are infected with tuberculosis. Most have latent, or inactive, cases. They do not suffer coughing, increased body temperature or other signs of active TB.
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| A tuberculosis patient looks at a TB awareness poster in a 2007 photo |
But each year, about nine million people develop active cases and two million die. TB is an ancient bacterial disease. It can be cured with antibiotics, if patients take all their medicine. The victims, though, are mostly poor and live in developing countries.
Now, scientists have reported two new developments in tuberculosis research.
For the past century, a skin test has been the traditional way to identify latent TB. When cases are found, treatment can prevent many from becoming active. But the preventive drugs have a risk of side effects.
The skin test depends on the body's reaction to an injection of specially prepared TB protein. But the test often falsely identifies people as having latent TB if they have been vaccinated against the disease.
To avoid needless treatment, scientists have developed a blood test. This test is designed to identify patients with a high risk of developing the active form of TB.
Ajit Lalvani from Imperial College London led an international team in developing the blood test, called ELISpot (EL-ee spot). A study showed that the ELISpot blood test identifies latent TB while giving fewer false positive results.
The researchers say the ELISpot test has been recommended for use in about twenty countries worldwide. A report on the new blood test appeared last week in the Annals of Internal Medicine.
In another development, scientists have reported a step toward a better vaccine against TB. One currently used is seventy-five years old.
The new experimental vaccine contains a weakened TB bacterium from a strain of the current vaccine. The scientists say that in their study, the experimental vaccine created stronger responses against TB than the traditional one.
But the new vaccine contains an antibiotic-resistant gene that the scientists do not want released into the environment. So the vaccine will not be tested further. But research will continue on a similar one that does not contain the gene.
Daniel Hoft of the Saint Louis University School of Medicine in Missouri was lead author of a report in the Journal of Infectious Diseases.
And that's the VOA Special English Development Report. It was written by Jerilyn Watson.