A study published in the Veterinary Record on Friday shows that cats and dogs can get infected with the alpha variant of COVID-19 and develop symptoms of myocarditis, or heart inflammation, as a result.

In the U.K. study, two cats and one dog tested positive via a PCR test for the alpha variant. Another two cats and one dog displayed antibodies two weeks after developing signs of cardiac disease. Out of the 11 animals tested, none had any typical symptoms of COVID-19, but all had common indicators of cardiac disease.

The study clarifies that several of the pet owners had shown signs of respiratory illness weeks before their pets became sick or also tested positive for COVID-19.

Dr. Luca Ferasin, the lead author of the study, described the pets as “depressed, lethargic" and said that "they had either difficulty breathing because of accumulation of fluid in their lungs due to the heart disease, or they were fainting because of an underlying abnormal heart rhythm.”

There’s no evidence that other variants of the virus cause heart issues in animals.

“Our study reports the first cases of cats and dogs affected by the COVID-19 alpha variant and highlights, more than ever, the risk that companion animals can become infected with SARS-CoV-2,” said Ferasin.

“However, COVID-19 infection in pets remains a relatively rare condition and, based on our observations, it seems that the transmission occurs from humans to pets, rather than vice versa.”

Although most animals recover quickly from COVID-19, Margaret Hosie, a veterinary virologist at the MRC-University of Glasgow Centre for Virus Research, told NBC News that it is crucial to study the virus in pets as it's quite possible that the virus can mutate through them, which could potentially cause more acute disease in humans.

“Obviously we’re focused on preventing human-to-human transmission just now because that’s crucial, but if we were to take our eye off other species, we could be storing up problems in the future,” she said.

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