BOSTON (AP) – Four Massachusetts hospitals are asking hundreds of patients and staff to be tested for tuberculosis after learning a worker was diagnosed with the disease, health officials said.

Authorities said Thursday that a female surgical resident was contagious for six months and may have exposed more than 2,000 patients at the hospitals. She had shown symptoms of a chest infection in December, but the tuberculosis wasn’t confirmed until Monday.

Hospital officials are contacting patients who came in direct contact with the woman and requiring testing for employees who had close contact while the woman worked at Boston Medical Center, the Veterans Affairs hospital’s West Roxbury campus, Brockton Hospital and Cape Cod Hospital.

Boston Medical Center is requiring 750 of its roughly 4,000 employees to be tested, a hospital spokeswoman said. At least one-third of the 3,000 workers at the West Roxbury hospital also will be tested, according to Dr. Michael Charness, the hospital’s chief of staff.

John Rich, medical director at Boston Public Health Commission, which is leading the investigation, said patients have a lower risk of becoming infected than the woman’s co-workers, who spent more time with her. But officials said it could be weeks, if not months, before they know whether any others have been infected.

Dr. Keith Lewis, chief of anesthesiology at BMC, called tuberculosis “a very treatable disease” and said the risk to patients and employees was “very low.” Tuberculosis is a disease caused by bacteria that usually attacks the lungs and can cause weakness, weight loss, fever and night sweats.

Sue Etkind, director of the Division of Tuberculosis Prevention and Control at the Massachusetts Department of Public Health, said tuberculosis is difficult to diagnose. “A number of things could have been causing the same kinds of symptoms,” she said.

Worldwide, tuberculosis kills about 2 million people a year. Antibiotics can cure it, but treatment involves a regimen of up to four different drugs administered for six months. Many strains of tuberculosis also have become resistant to the available drugs.

The worker was diagnosed with an active form of tuberculosis, which means she was contagious and could have spread it to other people. However public officials said 90 percent of tuberculosis infections are latent, meaning patients don’t show symptoms and can’t spread the infection to other people.

No information on how the worker contracted the disease was released.

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