By STEPHANIE NANO Associated Press Writer December 5, 2002, 1:22 AM EST Screening and treating immigrants from developing countries for dormant tuberculosis infections would prevent thousands of cases and save tens of millions of dollars, a study shows. While the number of TB cases in the United States has been dropping, immigrants account for a growing proportion of them. There were nearly 16,000 U.S. cases last year and about half were in foreign-born residents, up from 27 percent a decade earlier. Potential immigrants now get a chest X-ray to detect active TB, and those who are sick are required to...