In two batteries of skin tests last month, given to 765 fresh processing employees at the Decatur, Ala., plant owned by Wayne Farms LLC by the State Department of Public Health's Tuberculosis Control Division, 28 percent were found to be infected, including one with active tuberculosis disease, which is contagious. Doctors have yet to evaluate X-rays for 165 current workers who tested positive to determine if any more are contagious.

The testing was prompted by an earlier active TB case – a former Wayne Farms worker.

Both employees with active TB are Hispanics born in countries where the disease is prevalent, heath officials said.

When the disease is latent, those with TB are not contagious, but the TB bacteria remains in the body for life unless it is treated. Once it becomes active it may cause permanent damage to the lungs and other organs and the airborne bacteria is easily spread by coughing, laughing or even talking. According to the Centers for Disease Control, 50 percent of those who have close contact with someone with active TB for 15 minutes will become infected.

Accompanied by the rise in illegal immigration, tuberculosis is making a comeback in the U.S., often eluding diagnosis by doctors who are unfamiliar with the disease.