Is tuberculosis contagious?

Is tuberculosis contagious? - The people of the entourage of patients infected with contagious tuberculosis are most at risk of TB infection, and when they were infected, it was in the period immediately following infection have the greatest risk of developing TB disease [1] . These two fundamental elements of the epidemiology and natural history of tuberculosis justify the priority of case detection of TB infection and TB disease in the entourage of a tuberculosis patient who was recently diagnosed.

The family is not the only favorable environment for the transmission of the tubercle bacillus. Communities reproducing crowded conditions quite similar to family promiscuity are multiple. Some of them can bring together people particularly vulnerable (young children, adolescents, immunocompromised patients or, increasingly, people infected with HIV), which justifies special vigilance. In the current epidemiological situation in France, where the incidence of tuberculosis has become relatively low [2] , screening “target” becomes important.

The objectives of the investigation are first to identify persons who may be sources of infection and treat them to interrupt the chain of transmission, then identifying recently infected people and offer them the appropriate chemoprophylaxis (preventive therapy) to prevent their infection is changing in the short term to TB disease. In a community, it takes more than assess the risk of transmission and highlight the potential factors causing the transmission to adapt preventive measures.

This text aims to provide a guide for the conduct of investigations when a case of tuberculosis or TB infection was identified in a family or community to. It does not affect the regular monitoring of personnel (such as hospital staff) particularly exposed to the risk of transmission, which is the subject of specific recommendations.

A tuberculosis is confirmed in a patient when culture showed the presence of tubercle bacilli ( Mycobacterium tuberculosis or bovis africanum ) [3] . However, in a proportion of cases (one third in France according to data from the mandatory reporting [4] ), bacteriological confirmation is not obtained and commissioning treatment is decided on clinical and radiological findings.

A Tuberculosis is contagious if there are tubercle bacilli in sputum. Tuberculosis is so contagious in its pulmonary form [1] . Extrapulmonary forms (bone, lymph nodes, urogenital, pleural, meningeal …) are exceptionally contagious. In practice, the contagiousness is defined by the presence of acid-fast bacilli (AFB) in the direct microscopic examination of sputum. Contagiousness is much lower if direct microscopy of sputum examination is negative and only the culture is positive  .


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