Self-Study Modules on Tuberculosis
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Module 1: Transmission and Pathogenesis
Answers To Case Studies
1.1. A 30-year-old man visits the health department for a
tuberculin skin test because he is required to have one before starting
his new job. He has a positive reaction to the tuberculin skin test.
He has no symptoms of TB, and his chest x-ray findings are normal.
- Should this be considered a case of TB?
The man described above has TB infection, and he has no evidence
of TB disease. Therefore, this is not a case of TB.
- Should this man be considered infectious?
No, he should not be considered infectious. This man has TB
infection, not TB disease. People with TB infection and no evidence
of TB disease are not infectious. (Note that sputum tests were
not done. Sputum tests are not necessary when a person has no
symptoms of TB and has normal chest x-ray findings. However,
if they had been done, we would expect them to be negative.)
1.2. A 45-year-old woman is referred to the health department
by her private physician because she was found to have TB infection.
She is an obese woman who has high blood pressure and heart problems.
Upon further questioning, she reports that she has injected illicit
drugs in the past but has never been tested for HIV infection.
- What conditions does this woman have that increase the
risk that she will develop TB disease?
One condition is injection of illicit drugs. This condition
increases the risk that TB infection will progress to TB disease.
Another possible condition is HIV infection. This woman is at
risk for HIV infection, which is the strongest known risk factor
for developing TB disease. This woman should undergo HIV counseling
Obesity, high blood pressure, and heart problems are NOT risk
factors for TB disease.
Released October 2008
Centers for Disease Control and Prevention
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Division of Tuberculosis Elimination - http://www.cdc.gov/tb
Please send comments/suggestions/requests
CDC/Division of Tuberculosis Elimination
Communications, Education, and Behavioral Studies Branch
1600 Clifton Rd., NE - Mailstop E-10, Atlanta, GA 30333