Evidence of the first documented cases of tuberculosis spreading to humans from cats has been found in the U.K. after officials say two people developed the disease following contact with felines.

The two human cases were reported in the English counties of Berkshire and Hampshire, reports BBC News. Both people are seeking treatment, but Public Health England maintain that the risk of humans contracting TB from cats remains “very low.”

Two additional people were found to have latent TB after being exposed to the disease, but didn't develop TB any further, report James Meikle and Louis Degenhardt at the Guardian. The outbreak was flagged at a veterinary practice, which then offered to screen people for the disease. 24 people out of 39 accepted the screening.

The Mycobacterium bovis infection, or M. bovis, also causes TB in cattle and other livestock animals. Breathing in or ingesting bacteria from through contamination of cuts while handling infected animals or carcasses is how humans contract the disease. The U.K. outbreak involved nine cats belonging to nine separate homes.

"These are the first documented cases of cat-to-human transmission, and so although PHE has assessed the risk of people catching this infection from infected cats as being very low, we are recommending that household and close contacts of cats with confirmed M. bovis infection should be assessed and receive public health advice," Dr. Dilys Morgan, an official at Public Health England, told the BBC, adding that M. bovis is still uncommon in cats.

The findings were reported in the Veterinary Record on Thursday. While TB caused by M. bovis infected tens of thousands of people in the U.K. every year during the 1930s, today only around 40 Britons a year are diagnosed, reports the Guardian.

Fewer than 30 cats had TB between 2006 and 2012, but research suggests that more cats than previously thought had the disease, and the numbers reported are underestimated. Six of the nine cats identified with the disease died from it.