Experts said animal tuberculosis is a greater threat to humans than previously believed. A report published Friday in the journal the Lancet Infectious Diseases called for action in battling zoonotic tuberculosis.

Tuberculosis is one of the world’s deadliest diseases, claiming at least 1.5 million lives worldwide in 2014. Animal tuberculosis is spread through contaminated food primarily raw or unpasteurized milk. It is more difficult to treat.

According to the U.S. Centers for Disease Control and Prevention, in many cases, doctors may not be able to differentiate between animal tuberculosis caused by Mycobacterium bovis and human tuberculosis caused by Mycobacterium tuberculosis. Animal tuberculosis is also resistant to the antibiotic pyrazinamide used to treat tuberculosis.

Institutions like the World Health Organizations have long been saying that the threat of animal tuberculosis has been ignored. Apart from contaminated food, people in contact with infected animals like veterinarians, butchers, dairy farmers can also be infected.

Francisco Olea-Popelka from the International Union Against Tuberculosis and Lung Disease said animal tuberculosis was “far more common than previously recognized.”

Estimates say there are about 121,000 cases of zoonotic tuberculosis every year. This is, however, a tiny fraction of the total number of tuberculosis cases every year.

“This is a well-known problem and has been neglected for decades, it is a disease that is preventable, treatable and curable and yet still today we have hundreds of thousands of people suffering from it,” Olea-Popelka told BBC. “Ten thousand die every year from this disease, that’s a lot of cases compared to many other diseases, why not care?”

Different studies give different estimates of how many cases of tuberculosis are actually animal tuberculosis cases. One study, quoted in the report, says 28 percent of all tuberculosis cases are animal tuberculosis cases, while another puts the number at 9 percent. A study that focused on tuberculosis in children said 45 percent of all cases are animal tuberculosis cases.

Studies in Mexico suggest 28% of all tuberculosis cases are down to zoonotic TB but a study in India put the figure at 9% and one in children in California suggested a figure of 45%.

“With approximately nine million individuals contracting TB globally each year, even relatively low percentages of zoonotic TB lead to large numbers of people suffering from this form of the disease,” Paula Fujiwara from the International Union Against Tuberculosis and Lung Disease said. “People living with zoonotic TB require specialized care, but in the vast majority of cases, they are not even adequately diagnosed.”