Tuberculosis cases continue to fall in the United States, but some immigrants have disturbingly high rates of the disease, according to a study released Tuesday that called for more aggressive action.
TB rates were highest among residents from lower Africa and parts of Southeast Asia. Most drug-resistant TB cases also were from foreign-born residents, the study noted.
Rates of at least 250 TB cases per 100,000 were found among people from African countries such as Ethiopia, Kenya and Somalia and from Southeast Asian nations including Vietnam, Cambodia and the Philippines.
By comparison, the overall rate of TB in the U.S. is fewer than 5 per 100,000, according to researchers at the Centers of Disease Control and Prevention, whose study is based on data from 2001-06. Their findings are being published in Wednesday’s Journal of the American Medical Association.
Dr. Henry Blumberg of Emory University’s medical school, said the research shows “that it’s in the interest of the United States to try to enhance global TB efforts.”
Of those infected, drug-resistant TB was found in 20 percent of recent immigrants from Vietnam and 10 percent of foreign-born residents overall, compared with a little more than 4 percent of U.S.-born residents.
While most TB cases come from recent arrivals, a significant number involve people who have lived in the United States for at least 20 years, the study authors said. Most of these likely resulted from latent infections acquired years earlier abroad, they wrote.
[Editors Note: “Tuberculosis Among Foreign-Born Persons in the United States,” by Kevin P. Cain, et al. can be accessed on-line here. There is a charge.]
Context Foreign-born persons accounted for 57% of all tuberculosis (TB) cases in the United States in 2006. Current TB control strategies have not sufficiently addressed the high levels of TB disease and latent TB infection in this population.
Objective To determine the risk of TB disease and drug-resistant TB among foreign-born populations and the potential impact of adding TB culture to overseas screening procedures for foreign-born persons entering the United States.
Design, Setting, and Participants Descriptive epidemiologic analysis of foreign-born persons in the United States diagnosed with TB from 2001 through 2006.
Main Outcome Measures TB case rates, stratified by time since US entry, country of origin, and age at US entry; anti-TB drug-resistance patterns; and characteristics of TB cases diagnosed within 3 months of US entry.
Results A total of 46 970 cases of TB disease were reported among foreign-born persons in the United States from 2001 through 2006, of which 12 928 (28%) were among recent entrants (within 2 years of US entry). Among the foreign-born population overall, TB case rates declined with increasing time since US entry, but remained higher than among US-born persons—even more than 20 years after arrival. In total, 53% of TB cases among foreign-born persons occurred among the 22% of the foreign-born population born in sub-Saharan Africa and Southeast Asia. Isoniazid resistance was as high as 20% among recent entrants from Vietnam and 18% for recent entrants from Peru. On average, 250 individuals per year were diagnosed with smear-negative, culture-positive TB disease within 3 months of US entry; 46% of these were from the Philippines or Vietnam.
Conclusion The relative yield of finding and treating latent TB infection is particularly high among individuals from most countries of sub-Saharan Africa and Southeast Asia.
Author Affiliations: Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, Georgia.