The reasons behind a 19% drop in US tuberculosis (TB) cases among foreign-born people between 2007-2011 vary depending on the person's country of origin and when they entered the U.S., according to a study published February 10, 2016 in the open-access journal PLOSPLOS ONE ONE by Dr. Brian Baker from the U.S. Centers for Disease Control and Prevention and colleagues.
While the overall number of TB cases in the U.S. has declined over the past two decades, TB morbidity among foreign-born people remains persistently elevated. Beginning in 2007, scientists observed a sharp decline in TB cases among recent U.S. entrants. The authors assessed whether this decrease was because of changes in population size or through decreased incidence of TB. Specifically, they looked at TB case counts, TB case rates, and population estimates by time since U.S. entry, using the U.S. National Tuberculosis Surveillance System and the American Community Survey.
During 2007-2011, there was an overall 19% decline in TB cases among all foreign-born people in the U.S. The authors found that TB cases decreased in recent entrants from each of the top five countries with largest number of cases diagnosed in the U.S.: Mexico, Philippines, India, Vietnam, and China. However, the causes for the decline varied by country of origin; among recent entrants from Mexico, 80% of the decline was attributable to a decrease in population, while the declines among recent entrants from the Philippines, India, Vietnam, and China were almost exclusively the result of decreases in TB case rates. The authors also observed an unexpected decline in TB cases during 2007-2011 among non-recent entrants, who account for ~75% of TB cases among the foreign-born each year. The authors suggest that strategies that will impact both recent and non-recent entrants are necessary to further reduce TB morbidity in the U.S.
"These results are important because they help guide future TB control strategies. To accelerate the decline of TB in the U.S., it will be important to invest in TB control overseas as well as provide testing and treatment to those with TB infection among the ~43 million foreign-born persons currently living in the U.S."