An outbreak of Mycobacterium tuberculosis in the Kansas City area has become one of the largest recorded in the U.S. in recent years, with 67 active cases confirmed in Wyandotte and Johnson counties, according to the Kansas Department of Health and Environment.

The outbreak, which began in 2023, has no identified source. In addition to active tuberculosis (TB) cases, 79 individuals have been diagnosed with latent TB infection (LTBI) as of early 2024. Without treatment, LTBI can progress to active TB at any time.

TB is primarily transmitted via airborne droplet nuclei and typically affects the lungs but can involve extrapulmonary sites, including the brain. Untreated TB carries a significant mortality risk. Diagnosis of LTBI relies on interferon-gamma release assays (IGRAs) or tuberculin skin tests (TSTs), while active TB requires microbiologic confirmation.

The CDC has deployed four epidemiologists to assist with expanded contact investigations, targeted testing, and public health interventions. The Kansas Department of Health and Environment (KDHE) has not yet provided additional details on containment measures.

In 2023, TB replaced COVID-19 as the leading cause of infectious disease-related mortality worldwide, according to the World Health Organization. The U.S. recorded 8,649 cases in 2023, up from 9,606 in 2022.

The largest documented U.S. TB outbreak occurred between 2015 and 2017 in a Georgia homeless shelter, resulting in over 170 active cases and 400 LTBI cases. TB remains more prevalent among individuals who have lived in congregate settings or who have a history of travel to endemic regions.