() A “small number” of tuberculosis cases have been found at several Chicago migrant shelters, city health officials confirmed Thursday, adding to the outbreak of measles being experienced by new arrivals in the city.

A health department spokesman said that the agency became aware of the small number of tuberculosis cases in a “few different shelters”. The city said that an estimated 10-20% of residents of South and Central America have latent TB infection, the health department said in a statement released on Wednesday.

The infection is asymptomatic and is not transmissible to others, but it does result in a positive TB test, the statement said. At this time, city health officials said they do not consider the small number of cases a substantial threat to the public.

For those who do have active cases of tuberculosis, the Chicago Department of Public Health assigns a nurse case manager to each individual and performs a contact tracing investigation, spokesman Jacob Martin said.

Martin did not immediately return an email to on Thursday seeking information about how many cases have been confirmed and what how many migrant shelters in Chicago are affected.

According to the Centers for Disease Control and Prevention, tuberculosis is caused by a bacteria that attacks the lungs. But TB bacteria can attack any part of the body such as the kidneys, spine and brain. Not everyone who tests positive for TB will get sick, but if it goes untreated, it can become fatal, the CDC warns.

Tuberculosis is curable with antibiotics and is not particularly infectious, but typically requires several hours or more of prolonged close contact between individuals to spread. CDPH continues to take cases seriously to keep it contained.

As of Thursday, the city health department has not confirmed any reports of tuberculosis that resulted from exposure to someone inside one of the affected migrant shelters, the health department said.

Tuberculosis is not a novel or rarely seen illness in Chicago, health officials said, and the city health department typically expects to see between 100-150 cases of tuberculosis in Chicago residents in an average year.

The tuberculosis cases come as the city continues to see an increased number of confirmed measles cases, the majority of which are linked to Chicago’s largest migrant shelter. As of Thursday, there have been 56 measles cases reported in Chicago, including three cases this week.

A team from the CDC remains in Chicago to assist with the handling of the measles cases and is still investigating the source of how measles arrived in the city. Mayor Brandon Johnson and city health officials have said that migrants being housed in city-run shelters did not bring the virus to the city.

In its statement, Chicago health officials said that they will continue to offer treatment to individuals as necessary and take the proper precautions to eliminate the spread,