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Education Materials > Publications > Self-Study Modules on TB > Module 5 > Case Studies

Self-Study Modules on Tuberculosis

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Module 5: Infectiousness and Infection Control

Answers To Case Studies

5.1. For each of the following situations, decide whether the patient should be considered infectious or noninfectious, and explain why.
  • Mr. Lopez started TB treatment 7 days ago. He still has a cough. Two weeks ago, he had a sputum smear that was positive; since then no sputum specimens have been tested.

    Mr. Lopez should be considered infectious. He does not meet the criteria for noninfectiousness because (1) he has been receiving treatment for only 7 days, not 2 to 3 weeks, (2) his symptoms haven't improved, and (3) he doesn't have three consecutive negative sputum smears.

  • Ms. Nguyen, a patient with pulmonary TB, has been receiving TB treatment for 6 weeks, and she no longer has symptoms of TB. She has had three sputum smears done. The first one was positive, but the last two were negative.
  • Ms. Nguyen meets the first two criteria for noninfectiousness: she has been receiving treatment for at least 2 to 3 weeks and her symptoms have improved. However, she should be considered infectious until she has three consecutive negative sputum smears.

  • Mr. Martin started treatment for pulmonary TB in April. His symptoms went away and his sputum smears became negative in May. He missed his clinic appointment in June. When he returned to the TB clinic at the beginning of August, he was coughing.
  • Mr. Martin may have become noninfectious in May, but it appears that he may be infectious again. He is coughing, and the fact that he missed his June appointment may indicate that he has not been adhering to treatment. At this point, Mr. Martin should be considered infectious. He should be evaluated for infectiousness and nonadherence to treatment.

5.2. You are checking patients into the TB clinic. An elderly man comes to the desk and says he was told to come and get checked because one of his friends has TB. You notice that he looks sick and is coughing frequently. The waiting room is full of patients, and you know it will probably be more than an hour before the physician can see him.
  • What should you do?
  • You should suspect that this man has infectious TB. You should work with the clinical staff to ensure that he is evaluated for TB quickly. In the meantime, the man should be given a surgical mask, instructed to keep it on, and asked to cover his mouth and nose when coughing or sneezing. He should be placed in an area away from other patients right away.

5.3. You are sent to deliver directly observed therapy to a woman who started treatment last week for suspected pulmonary TB. Her sputum smear results are not back yet. You are asked to collect another sputum specimen while you are at the woman's home.

  • What precautions should you take?
  • First, you should instruct the patient to cover her mouth and nose when she coughs or sneezes. Second, because the patient may be infectious, you should wear a personal respirator when visiting her home. Third, you should collect the sputum specimen in a well-ventilated area (preferably outdoors), away from other household members. (Ideally, sputum specimens should be collected in a special isolation room or booth.) Fourth, because you visit TB patients at home as part of your job, you should participate in a TB screening and prevention program through your employer.


Released October 2008
Centers for Disease Control and Prevention
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Division of Tuberculosis Elimination -

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