The San Francisco City Department of Public Health will be returning to campus soon to re-screen students potentially exposed to tuberculosis late last semester.

The health department’s TB investigation occurred when the second of two known tuberculosis cases at SF State last year was discovered in late November. More than 250 students, faculty and staff were considered to be at “significant risk.”

Announcements were made in the classrooms shared with the infected ethnic studies student, and on the Student Health Services Web site, while individual letters sent by the health department notified those who may have been exposed to the highly treatable bacterium.

While a free screening was offered on campus during finals week, the health department said they are stressing the importance of a second screening after a three-month incubation period. They project a return to campus in late February or early March to test those who originally yielded negative TB results.

“It’ll be the final test and make sure they’re not infected,” said Tom Hoynes, senior disease control investigator of the city’s health department.

Six of more than the 150 tested yielded positive tests, which Hoynes called a “really low rate.” A positive skin-test means they may have been exposed at some point in their lives, but there is no indication of recent exposure, nor are these specific cases active, Hoynes said.

San Francisco currently ranks within the top 5 of the nations highest TB infection rates, according to Hoynes. He added that one in three San Franciscans would yield positive skin tests.

If the airborne infection develops into disease, some of the symptoms are drenching night sweats, dramatic weight loss and consistent coughing, which commonly force those infected to seek medical help. Cases are then reported to the public health department and investigated.

Interviews with the infected patient lead to those at “significant risk” - anyone who may have shared 12 hours of air with the patient, even if its once or twice a week for an hour, over the course of a semester, Hoynes said as an example.

But Hoynes said TB is relatively difficult to transmit and slow in progressing.

Treated with antibiotics as a preventative measure over a period of six months, positive patients have a 10 percent chance of developing the disease in their lifetime. Though some strains of the bacterium have recently become drug resistant, rarely does the disease lead to surgery or death in the United States.

Hoynes said the legacy of TB is an endemic and a “massive problem” in some developing regions including Africa, South East Asia, Central America and the former Soviet bloc.

For this reason, patients are often foreign born, as was the case with the student last spring.

“It’s highly, highly, highly likely you got it from a previous source,” SF State Health Educator Albert Angelo said referring to TB’s often-foreign beginnings.

Angelo said there was a lot of unnecessary fear generated by the media attention to the case, which was of concern, but nothing to panic about. He also said it was handled according to governmental and university protocol.

Because the two infected students are connected by some time spent in the same building, the state of California is performing genetic testing to identify the specific strains of TB and will then be able to confirm whether or not the spring and fall cases are derived from the same origin.