Five babies have tested positive for the tuberculosis infection at a hospital in El Paso, Texas, where its suspected an infected worker possibly exposed hundreds of newborns to the disease, health officials said.

The El Paso Department of Public Health increased the calculated number of total individuals to 858 who may have been exposed to the potentially fatal disease.

The agency earlier in the month announced 706 babies and 43 employees were believed exposed to the infected worker between September 2013 and August 2014, said a report by Reuters.

"It is important to point out that they [the babies] are not considered to have active TB disease," a health department statement said of the five who tested positive.

Tuberculosis, which generally affects the lungs, is spread when an infected person coughs, sneezes or speaks and can remain dormant in a person's body for months or years, according to the United States Centers for Disease Control and Prevention.

The infected employee, working in a nursery at Providence Memorial Hospital in El Paso, interacted with patients for months before being diagnosed with the disease, the department said.

Health and hospital officials were working to contact the affected families and say families will be provided screening and follow-up care free of charge.

The hospital reportedly sent letters to the parents of children born between September 2013 and Aug. 16 of this year, notifying them of the active case at the hospital.

"Your child will also need a chest X-ray so that a doctor can check to see if your children's lungs are clear," according to the letter parents received.

Providence Memorial Hospital delivers approximately 3,000 babies a year and is the hospital of choice for many of the region's families.

Babies are at higher risk for contracting TB, but because their lungs are so small, they do not spread the disease easily, according to health authorities.

The El Paso Health Department said parents are not being advised to get tested because they did not come in close contact with the hospital employee, who worked in the nursery.

Parents have to wait up to 72 hours to get their children's results.