Cause of cat coronavirus outbreak uncovered

Researchers have uncovered the mystery behind the deadly cat coronavirus outbreak that swept through Cyprus in 2023. They found it was resultant from a new hybrid virus - part cat coronavirus, part dog coronavirus. This is the first study that shows cross-species “mix and match” genes can create dangerous new strains in cats.

A stray cat, lazing on the street in Ayia Napa, Cyprus — A stray cat on the street in Ayia Napa, Cyprus

Coronaviruses don’t just affect people – they also infect many animals, including cats and dogs. Normally, feline coronavirus (FCoV) only causes mild stomach issues in cats, but sometimes it mutates into a deadly version called Feline Infectious Peritonitis (FIP).

In 2023, vets in Cyprus noticed a sudden explosion of FIP cases, far beyond the usual levels. Veterinarians reported thousands of sick cats, and within months, over 10,000 cats showed signs of the disease. Alarming new cases even appeared in the UK, linked to cats imported from Cyprus.

A graph showing a spike in cat FIP cases in 2013 — There was a sudden explosion of FIP cases in 2023 due to FCoV-23 outbreak

To understand what was driving the outbreak, an international team led by Dr Charalampos Attipa, researcher at the IRR and The Royal (Dick) School of Veterinary Studies, collected samples from infected cats and sequenced the virus’s genetic material.

Their analysis revealed something surprising: the new virus, called FCoV-23, was a genetic hybrid of a cat coronavirus and a dog coronavirus. This was the first time such a hybrid had been documented. By combining genetic code from both species, the virus gained the ability to spread rapidly between cats and often caused fatal FIP.

This is the first time we document a cat coronavirus combined with a dog coronavirus in a way that made it much deadlier and easier to spread. It shows how viruses can “mix and match” genes to create dangerous new versions that can cause outbreak and even pandemics.

These findings matter for both animal health and human health. This study highlights how easily new and dangerous strains can emerge when viruses cross species boundaries. While FCoV-23 only affects cats, the outbreak underscores the importance of tracking animal viruses closely, especially since some coronaviruses have the potential to cross into humans.

The researchers continue to monitor the situation and will use established FIP treatments to cure the diseased cats from FCoV-23. Next, they want to find out how exactly this hybrid virus works, spreads and causes sickness to cats. They will aim to develop vaccines and better treatments to stop it spreading beyond other countries.

This research, led by the Royal (Dick) School of Veterinary Studies and involving other key authors from the School, can be further read about on the vet school website.

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