Pets can harbor virulent antibiotic-resistant infections and spread them to humans, German researchers reported on Wednesday.

The warning is based on the case of a woman who had deep abscesses caused by methicillin-resistant Staphylococcus aureus or MRSA. Her husband and two children showed evidence of infection, too, but it disappeared with treatment even as the woman’s abscesses festered.

So Dr. Andreas Sing of the Bavarian Food and Health Safety Authority and colleagues examined the woman’s three apparently healthy cats. One turned out to have the same strain.

Only after the cat was treated with antibiotics did the woman’s abscesses clear up.

Researchers already know that people can pick up such infections from dogs.

“It remains unclear whether the cat was the source of the patient’s infection or vice versa,” the researchers note - but said the strain was rare in humans.

“This case illustrates that MRSA transmission also occurs between humans and cats,” they added in a letter to the New England Journal of Medicine.

“We conclude that pets should be considered as possible household reservoirs of MRSA that can cause infection or reinfection in humans.”

BOSTON (Reuters )