TB is different from many other bacterial infections in that disease can be caused by either reactivation of latent infection acquired years earlier or as a result of recently acquired infection followed by rapid progression to active disease. TB cases due to recently acquired infection--or clustered cases--indicate the amount of transmission that is occurring within the population, while non-clustered cases provide an index of TB resulting from reactivation of latent infection, in which a person was infected many years earlier.
Previous studies have shown that DNA fingerprinting of the TB bacteria allows tracking of specific strains. With this information the research team was able to determine patterns of how different strains moved among population groups causing TB.
"In San Francisco we had detected a sizable amount of transmission of TB in the early 90s, so TB control measures were established that focused on halting the spread of TB and especially reducing the number of clustered cases. The intensified TB control measures focused on preventing transmission and on the use of effective preventive therapy," Jasmer said.
Measures included improved communication between TB control investigators and populations at risk, such as the homeless and substance abusers; expanded use of directly observed therapy, in which health care workers supervise the care of TB patients; development of an HIV-related TB prevention program; improved screening among persons in residential care facilities, jails, and homeless shelters; and improved hospital infection control measures.
"Although we have made considerable progress in decreasing the rate of cases and
especially those cases due to recently acquired infection, there is still a
large pool of persons infected from the extensive transmission of the previous
15 years. We are focusin
Contact: Corinna Kaarlela
University of California - San Francisco