Simply tracing one exposed person to the next is not an accurate way to follow the spread of tuberculosis, Norwegian researchers report. Instead, formal genetic testing, or “genotyping,” is needed.

Reporting in the medical journal Thorax, Dr. Ulf R. Dahle, at the Norwegian Institute of Public Health in Oslo, and colleagues present the findings following a tuberculosis outbreak that occurred in 2003 involving 15 recent immigrants in the same community. All 15 had social contact with each other and 13 belonged to the same church.

Standard survey and culture techniques gave an incomplete picture of how the outbreak involved. Genotyping testing was needed to fill in the blanks.

The authors emphasize that “traditional contact tracing needs confirmation by genotyping before transmission patterns of M. tuberculosis can be conducted…especially between patients with several risk factors for infection.”

SOURCE: Thorax, February 2005.