Story highlights A woman with tuberculosis may have spread the infection at a hospital

She gave birth to twins, one of whom was later diagnosed with tuberculosis

The woman and her babies all died this summer

The health district is investigating other potential cases

Health officials have identified about 140 infants who may have been exposed to tuberculosis this summer at a hospital in Nevada.

A young mother who gave birth to premature twins had the bacterial infection, according to the Southern Nevada Health District. The woman died, as did both her babies, at least one of them from tuberculosis.

Southern Nevada Health District officials believe the mother contracted tuberculosis from eating unpasteurized dairy products from Mexico, although there is no proof of this, said Dr. Joseph Iser, the health district's chief health officer.

The mother could have exposed at least one of the infants to tuberculosis while in the neonatal intensive care unit at Summerlin Hospital, but Iser and his colleagues believe it is more likely the infection was transmitted at or around the time of birth.

One of the infants died in June and was buried before the bacterial infection was suspected.

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The mother was transferred to a hospital in a different state, while the surviving baby stayed in the NICU at Summerlin. The mother died of tuberculosis in July.

"We were informed of her death of tuberculosis, and immediately we contacted (Summerlin) hospital," Iser said. "The hospital immediately put the surviving twin into isolation to prevent transmission. The hospital did the right things once they knew that tuberculosis was a possibility."

The second twin died of tuberculosis in August.

An initial investigation of hospital employees who might have been exposed, as well as close contacts of the mother, revealed two cases of active tuberculosis: one in a hospital staff member and one in a family member. Both of them are receiving treatment, Iser said.

An additional 24 people were found to have latent tuberculosis, which means that the bacteria are in the body but don't cause symptoms and are not contagious. About 5% to 10% of people with a latent infection will develop active tuberculosis disease at some point in their lives, according to the Centers for Disease Control and Prevention

The heath district has offered treatment to these 24 people with latent cases.

Tuberculosis is a bacterial infection that is spread through droplets in the air when infected people cough or sneeze. The disease often affects the lungs, but it can also impact the brain, kidneys or spine, according to the CDC.

Symptoms of tuberculosis include loss of appetite, night sweats, chills, fatigue, fever and unexplained weight loss. In the lungs, the disease may cause coughing for three weeks or longer and chest pain. Patients may even cough up blood.

Treatment may involve multiple drugs, depending on the strain. Common medications include isoniazid, rifampin, ethambutol and pyrazinamide, according to the Mayo Clinic

The Nevada investigation has been broadened to look for others who may have come in contact with the dangerous bacteria. The families of about 140 infants who could have been exposed are being asked to be tested. These babies could have been exposed between May 11 and August 8, according to CNN affiliate KTNV

"I really don't expect to find any more cases at all," Iser said. "But again, we're testing and offering to test all of these infants and their parents now."

The health district is not certain whether the infant who had confirmed tuberculosis had spread the bacteria, or if it was the mother when she visited the NICU.

"In infants this young, they often don't have symptoms, and they often aren't very infectious," Iser said.

Babies who have had exposure to someone with an active case of the infection would have a small risk of contracting the infection themselves, but the health district recommends tuberculosis testing for those babies and parents, Southern Nevada Health District said in a statement.

Parents of the babies in the NICU received a letter in August from the health district that described the investigation and its early results.

Anyone who was visiting other parts of the hospital at the same time, such as "going through the lobby, going up to visit their relatives in pediatrics or the adult wing of the hospital, would not have been exposed to tuberculosis," Iser said.

"We will contact those people at risk who we identified through hospital records," Iser said.