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. 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.
For the past century, a skin test has been used 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
An international team developed 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.
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 their study showed that the experimental vaccine created
stronger reactions 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 future tests of the vaccine are