Tuberculosis once ravaged the country, but has largely been on the decline in recent decades. According to a report from the Washington Post, however, the Centers for Disease Control and Prevention recently reported that an alarming number of states are experiencing an uptick in the disease for the first time in almost 25 years.

29 states and the District of Columbia each had more TB cases reported in 2015 than in 2014, raising concerns that we may be losing control of one of the most dangerous diseases to ever affect the human population. So far, however, nobody has been able to give a reason for the increase in TB cases in the U.S.

While the increase in TB cases was relatively small, with an additional 157 cases reported throughout the country, it is still cause for concern. The total number of cases in the U.S. in 2015 was 9,563, two-thirds of which were linked to people who were born in other countries. People of Asian descent accounted for the majority of the cases (3,007), while Caucasian Americans reported the disease at a rate of 0.5 cases per 100,000 people.

“After two decades of declining incidence, progress toward TB elimination in the United States appears to have stalled,” said CDC officials. Among the biggest factors contributing to the recent uptick, researchers say, is stalled funding for TB research. The disease can be difficult to prevent for low-income populations who are disproportionally affected by substance abuse, incarceration and homelessness, and other diseases.

Tuberculosis is caused by airborne bacteria that enter the body through the lungs. It spreads rapidly between people, but can lie dormant without showing symptoms for years. According to the latest CDC estimate, roughly 11 million Americans carry the dormant form of the disease. It can be treated with antibiotics, but this can be costly and time-consuming.

While officials have reason to be worried, the levels of TB in the U.S. remain a fraction of what they were in the 19^th and 20^th centuries.

A press release from the CDC describing the latest trends in TB in the US can be found here.