Extensive transmission of Mycobacterium tuberculosis from 9 year old child with pulmonary tuberculosis and negative sputum smear

Patients with pulmonary tuberculosis and either a positive sputum smear or cavitating pulmonary lesions have been considered to be infectious1 as these indicate higher bacterial load accumulating with longer duration of infection. The source of infection in outbreaks among children is usually an adult with these features.2 Children have been considered less likely to transmit infection because they were unlikely to expectorate infective droplet nuclei. In the absence of a positive sputum smear, guidelines do not recommend screening of wider contacts in addition to household contacts,3 although in the United States, contact screening is recommended if resources are sufficient.4 Here, we report extensive transmission of tuberculosis in a junior school in Luton, England, from a child with pulmonary tuberculosis in whom a sputum smear was negative.