A hospital in San Jose, Northern California said that hundreds of babies, mothers and employees in its facility may have been exposed to tuberculosis after one of its nurses was confirmed to have contracted the illness.

The Santa Clara Valley Medical Center nurse who was diagnosed of active tuberculosis may have placed 350 infants at the hospital's newborn nursery at risk along with 368 mothers and 338 employees.

A spokesperson for the hospital said on Friday, Dec. 11, that the employee was placed on leave in mid-November before the diagnosis was confirmed.

The infected nurse was tested in September but the results were negative. A screening for an unrelated medical condition, however, revealed that the nurse has tuberculosis. It is believed that the employee is not terribly contagious since she does not exhibit symptoms and has no cough.

The center's head of pediatrics Stephen Harris said those who have come in contact with the nurse need to undergo testing for the potentially fatal disease.

All infants born at the center between August and November also need to go through an antibiotic treatment for six months as precautionary measure even if they do not test positive for the disease.

"With babies, we need to be more cautious because the disease is more serious," Harris said. "Babies have an immature immune system, the bacteria can get into their bloodstream. From the bloodstream it can go everywhere in the body, including the brain."

Officials started notifying parents last week. The calls were delayed for weeks because the hospital went through the lengthy process of reviewing the work locations and shift schedule of the employee. The staff also needed to come up with a list of babies and mothers that the nurse came into contact with and doctors sought the advice of TB experts on the benefits of using antibiotics and chest X-rays on young patients.

Of the infants affected, the oldest were a little over three months old and the youngest could be between three to four weeks old.

Tuberculosis was once the leading cause of death in the U.S. It is caused by the bacterium Mycobacterium tuberculosis that targets the lungs. Infected individuals could spread the disease through laughing, singing and talking since these entail a great deal of contact.

Symptoms of active TB of the lungs include coughing sometimes with blood or sputum, weight loss, chest pains and night sweats.