SAN JOSE -- More than 1,000 people, including 350 infants, may have been exposed to tuberculosis this fall after a nurse at a Northern California hospital was diagnosed with the disease, CBS San Francisco reports.

The hospital was notified in mid-November that the nurse received the diagnosis after the nurse's primary care doctor conducted a screening for an unrelated medical condition, officials at Santa Clara Valley Medical Center said Friday.

The nurse and all other hospital employees are screened for tuberculosis once a year, and the nurse's test in September came back negative, hospital officials said.

The nurse received the diagnosis after the September test results were in.

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Those at greatest risk of exposure in this incident are infants, mothers and hospital employees, Santa Clara Valley Medical Center Chair of Pediatrics Dr. Stephen Harris said.

Hospital officials have identified 1,056 people at greatest risk, a number made up of the 350 infants, 368 mothers and 338 employees, Harris said.

Infants face severe possible consequences from the disease, including death, Harris said.

"It can be life-threatening," he said.

Unlike in toddlers and adults, the infection in an infant can get into the bloodstream and spread to other parts of the body, he said. In toddlers and adults the infection stays in the lungs, he said.

The disease tends to smolder for months before becoming deadly, though diagnoses are often made late, Harris said.

Hospital officials spent a month preparing to notify people of the potential exposure because officials had to consult with experts on, among other things, the window in which the exposure may have taken place and treatments, Harris said.

"We're confident we're addressing the situation with great speed," he said.

The infants and mothers potentially exposed were in the medical center's Mother & Infant Care Center between mid-August and mid-November, hospital officials said.

The work to notify the mothers and parents of the infants has begun, but not all have been notified, Harris said. The officials are notifying parents by mail and by phone, he said.

Visits for screenings and treatment will begin Monday, Harris said.

Harris said hospital staff will be talking with each parent about the need to treat their infant with the daily antibiotic isoniazid for six to nine months to prevent infection.

"That's a big deal," Harris said. "That is not something to be taken lightly."

The antibiotic kills tuberculosis and can prevent the infant from becoming ill, hospital officials said.

Harris said isoniazid is effective at preventing tuberculosis from setting up shop in both infants and adults.

None of the 1,056 people potentially exposed will have to pay for screening or treatment, hospital officials said. The cost will be picked up by the medical center, which is owned and operated by the county.

Mothers and employees will be screened and treated, if needed, with the same antibiotic as the infants for the same period of time.

Harris said the likelihood anyone was exposed is low because the nurse with the disease had no symptoms. She was not sneezing or coughing, two ways the disease is spread, hospital officials said.

Only active tuberculosis can be spread, Santa Clara County Health Officer Dr. Sara Cody said. Inactive or latent tuberculosis can reside in the body for a period of time and then become active again, health officials said.

Of the 1,056 people potentially exposed, no one has reported an infection, hospital officials said.