Background: Conventional contact investigation and molecular fingerprinting of Mycobacterium tuberculosis isolates in tuberculosis (TB) outbreaks have facilitated recognition as well as application of public health control activities. Singing in a choir as an activity that promotes TB transmission has been occasionally recognized. Such avocational transmission in a middle class community can occur with attendant difficulties encountered in contact investigation.
Methods: Five cases of TB (one index case; three secondary cases; one unassociated case) were identified among members of a famous church gospel choir in Newark, NJ. DNA fingerprinting and susceptibility testing were done on all retrieved strains. Of 306 choir members who had tuberculin tests, 19% were reactors. The presumed outbreak site was investigated.
Results: Four of the five patients were tenors, and one was an alto. Tenors were approximately twice as likely to be tuberculin reactors than subjects with other vocal ranges combined (relative risk, 2.04; 95% confidence interval, 1.17 to 3.56). An air ventilation outlet was directly in front of the tenor section. Some limited extra-church activity between choir members may have contributed to transmission.
Conclusion: Conventional contact investigation must be supplemented by newer techniques, such as DNA fingerprinting, in identifying possible outbreak transmission. Singing, location of a ventilation outlet, and exposure time may have contributed to TB transmission in this outbreak. Transmission need not only be in congregate settings among well-defined socioeconomic groups but may occur unexpectedly in middle class communities.