However, researchers reported in the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society, that the rate of tuberculosis continues to be far higher in foreign-born residents -- even those who have been in the country for more than five years -- than among native-born citizens.

"For example, in 2004, a total of 14,517 cases of tuberculosis was reported," said Kevin Cain, an internal-medicine physician at the International Research and Programs Branch of the Centers for Disease Control and Prevention in Atlanta. "Of these cases, 3,444 or 24 percent were foreign-born persons who had entered the United States more than five years previously."

Paradoxically, the need to expand testing comes at a time when budgets for tuberculosis prevention are being cut, David Cohn, professor of infectious diseases at the University of Colorado Health Sciences Center in Denver, told United Press International.

"This report indicates there is additional risk for patients who are foreign-born even after they have been living in the United States for more than five years," Cohn said. "The study results will be weighed before they are turned into recommendations, but for those doctors and communities who have resources, the evidence suggests it would be reasonable to extend testing to people who have lived here longer than five years."

Cohn said that most foreign-born immigrants are tested for active tuberculosis upon entry into the country. Latent tuberculosis testing may be performed when these individuals visit a physician as part of routine testing, but there are many who fall through the cracks, including, of course, long-term undocumented aliens who may eventually become candidates for citizenship through amnesty programs.

In 2004 there were 14,517 cases of tuberculosis reported in the United States; about 2.6 percent occurred in native-born Americans, while about 22 percent occurred in foreign-born individuals, Cohn said.

Cain collected data on all 2004 tuberculosis cases listed in the National TB Surveillance database. He and colleagues were investigating why the number of annual cases reported in U.S.-born persons declined by 93 percent from 1993 to 2004, while foreign-born cases increased by 5 percent. Overall, the rate of tuberculosis cases in the United States is 4.9 per 100,000 people.

The following countries of origin of U.S. immigrant residents had the largest number of tuberculosis cases in 2004: Mexico (1,976), Philippines (829), Vietnam (619), India (557), China (352), Haiti (248), South Korea (219), Guatemala (190), Ethiopia (169) and Peru (159).

"Twenty-five percent of all reported tuberculosis cases in the United States are among foreign-born persons who have lived in the United States for more than five years," said Cain. "There is no policy to test foreign-born persons for latent tuberculosis infection before entering the United States, or to test them after they have lived here for more than five years. As such, present guidelines do not currently address the burden of latent tuberculosis infection in the foreign-born subgroup."

The goal of tuberculosis control efforts in the United States is eliminating the disease -- or reducing the prevalence of the disease to less than one case reported per million in a given population. If achieved, the number of tuberculosis cases diagnosed in 2004 would have been less than 300.

"Until we address the burden of latent TB infection in the foreign-born group, achieving TB elimination will not be possible," said Cain.

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