acilli under control and the bacilli begin to multiply rapidly. This can happen very soon after infection or many yearsafter infection. About 10% of people who have the TB infection will developthe TB disease at some point, but the risk is greatest in the first year or twoafter infection.The tuberculosis disease usually occurs in the lungs (pulmonary TB), but can also occur in other places of the body (extrapulmonary TB). Miliary TBoccurs when tubercle bacilli enter the bloodstream and are carried to all parts ofthe body, where they grow and cause the disease to form in multiple sites.The infectiousness of a TB patient is directly related to the number of tubercle bacilli that he or she expels into the air. Patients who expel many tubercle bacilli are more infectious than patients who expel few or no bacilli. Patients are more likely to be infectious if they:* Have TB of the lungs or larynx* Have a cavity in the lung* Are coughing or undergoing cough-inducing procedures* Are not covering their mouth when coughing* Have acid-fast bacilli on the sputum smearThe infectiousness of the TB disease appears to decline very rapidly after adequate treatment is started, but how quickly it declines varies from patient to patient. Patients who have been receiving adequate treatment for 2 to 3 weeks, whose symptoms have improved and who have 3 consecutive negative sputum smears from sputum collected on different days can be considered noninfectious.Tuberculosis can be spread in many places, such as homes or worksites. TB can also be transmitted in health care facilities. TB is most likely to be transmitted when health care workers and patients come in contact with patients who have unsuspected TB disease, who are not receiving adequate treatment, and who have not been isolated from others. All health care facilities should take measures to prevent the spread of TB.There are four steps in diagnosing TB disease: medical history, tuberculinskin test, ch...
