Health officials are investigating a cluster of multi-drug-resistant tuberculosis cases in eight elderly Hmong residents in Ramsey County, but say the risk to the general public is low.

The outbreak first appeared in 2016, but just one case has been recorded this year and no new cases have been detected since state officials notified health care providers last month.

The individuals were probably exposed years ago, while living in refugee camps outside the United States, said Kris Ehresmann, infectious disease director at the Minnesota Health Department. Many people around the world get infected with tuberculosis, but it is not uncommon for the immune system to suppress symptoms, leaving the tuberculosis bacteria in the body in a latent state.

In about 10 percent of cases, the suppressed disease can become active, especially in those with chronic conditions such diabetes or kidney disease.

Tuberculosis is considered a transmissible disease, but it usually requires sustained exposure for someone to become infected. Places of exposure are usually school, work or home settings, rather than transient exposure in a public setting such as a store or on public transit.

“This is not at all a concern for general public,” said Ehresmann.

Although refugee health screening detected the latent TB cases when the individuals first immigrated to the United States, the standard drugs that were administered at the time apparently didn’t work.

“These people all completed recommended treatment,” said Ehresmann. “Because what they had was multi-drug-resistant, that wouldn’t have done the trick for them.”

Despite its label, this form of tuberculosis is treatable, but it requires second-line medications that are expensive and can take a long time to eradicate symptoms.

Minnesota had just five cases of multi-drug resistant TB between 2011 and 2015.

Because Hmong refugees are spread throughout the metro area and in other parts of the state, it is possible that new cases will be found outside Ramsey County in others who have a latent form of the disease picked up years ago.

Tuberculosis symptoms include coughing, sometimes with blood, chest pain, weight loss, fatigue, fever, night sweats, chills and loss of appetite.