NEW YORK - Hundreds of New York patients including newborn babies may have been exposed to tuberculosis by an infected hospital employee, city health officials said. The employee, whose identity was not disclosed, was diagnosed with active TB on Jan. 30, said Andrew Tucker, a spokesman for the city Department of Health and Mental Hygiene.

The department was notified of the case at St. Barnabas Hospital in the Bronx and has identified about 700 people who may have been exposed to TB, Tucker said. Of those, 532 were patients at St. Barnabas, including 238 infants.

St. Barnabas and the health department have reached out by mail and phone to 571 people, the hospital said. To date, 260, including 138 infants, have been tested for TB. Of those, three adults tested positive for exposure to TB, but no one has developed active TB, the hospital said.

TB is caused by a bacteria that usually attacks the lungs. It can be fatal if not treated properly. It is spread through the air from one person to another. Symptoms of TB infection include coughing, fatigue, loss of appetite, weight loss and coughing up blood.

The infected employee worked in the neonatal intensive care unit, the well-baby nursery, the maternity ward and the psychiatric ward.

Patients and staff members who were in any of those areas between Nov. 1 and Jan. 24, the last time the infected worker was in the hospital, are advised to call St. Barnabas at 718-960-3624.

The TB strain that the employee was diagnosed with is not the virulent drug-resistant type, but the fact that newborns were potentially exposed is cause for concern, officials said.

"Because their immune systems are not fully developed, newborns who are exposed to TB are at high risk of developing active TB," said Dr. Sonal Munsiff, the health department's assistant commissioner for TB control.

Munsiff said that even if they test negative for TB exposure, newborns who may have come in contact with the infected St. Barnabas employee should be placed on antibiotics as a precaution and then tested again at about 6 months of age.

After being treated for TB, the infected employee has tested negative for the disease but has not yet returned to work, said Fred Winters, a spokesman for St. Barnabas.

Tucker said no additional cases of active TB have been discovered.