By Will Dunham WASHINGTON, Dec 21 (Reuters) - A measles outbreak last year in Indiana in which 34 people became ill was spread by a 17-year-old U.S. girl who visited Romania without being vaccinated, U.S. health officials said on Thursday. The U.S. Centers for Disease Control and Prevention detailed the cause of the outbreak -- the largest in the United States since 1996 -- in an annual report on measles. CDC said there were 66 confirmed cases of measles in the United States in 2005, with no deaths. The 37 cases of measles in 2004 was the lowest ever recorded in the United States. The highly infectious, sometimes fatal viral illness has largely been eliminated in the United States by vaccination. Dr. Philip Gould of the CDC's Epidemic Intelligence Service said the 17-year-old girl was infected during travel lasting less than two weeks to Romania, where she did missionary work at an orphanage. Many of the people sickened in the outbreak had attended a gathering to welcome her back after her trip, Gould said, and most were unvaccinated school children. In all, one Illinois resident and 33 Indiana residents were sickened. "The reason why this outbreak in Indiana didn't become larger was in large part because the surrounding community was highly immunized," Gould said. "Physicians should continue to focus on immunizing their patients, especially those in higher-risk categories like international travelers, school-age children and health care workers," he added. Fifty of the 66 people who contracted measles in the United States last year were unvaccinated, CDC said. Seventeen were infected while traveling abroad. A smaller outbreak was traced to a 6-year-old visitor from Nigeria who was hospitalized in Ohio, and another limited outbreak occurred among people who had returned to Texas after a family reunion in Mexico, CDC said. Before the measles vaccine was introduced in the 1960s, there were about 450,000 measles cases and an average of 450 measles deaths annually in the United States.
