Public health officials say they've confirmed four additional cases of tuberculosis in Thunder Bay, Ont., about two weeks after notifying the public the disease was present in the city.

Eight cases have now been confirmed in Thunder Bay in 2018, according to the Thunder Bay District Health Unit, adding that most cases have occurred in individuals who lack adequate housing.

"We usually see one to five cases of active tuberculosis a year," Dr. Emily Groot, the health unit's associate medical officer of health was quoted as saying in a written statement. "A cluster of eight cases is unusual, and we are working closely with our social services and healthcare partners to identify additional cases."

Since public health officials are actively investigating, Groot told CBC News she expects more cases will be discovered in the coming weeks.

Still, the health unit maintains that the risk to the general public remains very low, as contracting the disease requires prolonged contact with someone who has the active form of tuberculosis. In those cases, it is spread through the air when an infected person talks, smokes, coughs or sneezes.

Crowded living conditions, inadequate nutrition and having a compromised immune system can increase the risk of contracting tuberculosis, the health unit said.

Symptoms of active tuberculosis include a cough, coughing up blood, chest pain, swollen lymph nodes, weight loss, fever and night sweats.

"Certainly this is unusual to have identified eight cases," Groot said. "But from a general public perspective, the risk is very low."