SANTA CLARA, Calif. — Three hundred and fifty infants were possibly exposed to tuberculosis at a California hospital by a hospital employee.

An additional 368 mothers or parents, and 308 employees were also potentially exposed, a spokeswoman said.

The Santa Clara Valley Medical Center in San Jose said it was notified in mid-November that one of its employees was suspected of having active tuberculosis. That employee, who worked in the area of the newborn nursery, was placed on leave.

“While the risk of infection is low, the consequences of a tuberculosis infection in infants can be severe. That’s why we decided to do widespread testing and start preventative treatments for these infants as soon as possible,” Stephen Harris, chair of pediatrics, said in a statement.

According to the Centers for Disease Control and Prevention, there were 9,421 cases of tuberculosis in the United States in 2014.

The illness is spread through the air when an infected person coughs, sneezes or spits and the germs are ingested by an uninfected person. It’s possible to be infected but not be ill from tuberculosis.

TB is treated with antibiotics for prolonged periods. If not properly treated, it can be fatal.

Santa Clara Valley Medical Center said that it was reaching out to mothers who were in its care between mid-August and mid-November and that it would be providing testing and preventative daily treatments for the infants.

Any mothers or parents and employees who were possibly exposed will be screened and, if necessary, provided treatment.

Most if not all of the employees have been screened already and there have been no positive tests so far, said spokeswoman Joy Alexiou.

The nurse who may have exposed others to tuberculosis underwent her annual screening in September, which was negative. Her physician later found her TB when she underwent evaluation for an unrelated medical issue, the hospital said.

The nurse’s condition was not immediately known.