Cats and COVID-19: More Frequent Exposure Than Expected

A study conducted between November 2021 and March 2022 in the Lisbon region (Portugal) reveals that nearly one-third of cats living in households where at least one person tested positive for SARS-CoV-2 developed antibodies against the coronavirus. These findings underscore the importance of including pets in epidemiological surveillance strategies.  

High Seroprevalence Among Exposed Cats

Of 76 cats from 50 human households with confirmed COVID-19 cases, 30.3% had detectable antibodies (ELISA test), and nearly 70% of these cases had neutralizing antibodies capable of inhibiting the virus in laboratory tests. In comparison, cats from the general population in Lisbon showed much lower rates: an overall seropositive rate of 14.7%, and only 20.4% had neutralizing antibodies. “This indicates real and repeated exposure of domestic animals to the virus in infected households,” the authors note.  

Variant-Specific Immune Responses

Analysis of the neutralizing capacity of feline sera revealed good efficacy against the alpha and delta variants, but a much weaker response to the omicron variant, which has since become dominant. This suggests that, as in humans, the evolution of the virus may limit the immune protection acquired by animals exposed to earlier strains. Contrary to initial hypotheses, the study did not find a significant link between exposure risk and human behaviors: neither sleeping with one’s cat nor the severity of the owner’s symptoms appeared to influence the results. However, the researchers acknowledge that larger-scale studies are needed to refine this assessment.  

A Global Trend

This Portuguese study is part of a broader trend. Other international studies report similar seroprevalence rates among pets in households with confirmed COVID-19 cases:

• in Europe, rates range from 21% to 53% depending on the country and time period;
• in the United States, approximately 27% of exposed cats and 33% of exposed dogs were seropositive;
• in Peru, a similar study confirms the impact of human infection on the health of domestic cats, thus indicating a reverse zoonotic risk.

Although there is no evidence that cats play an active role in human-to-human transmission of the virus, these findings support the idea of bidirectional vigilance: humans can infect their pets, which then develop an immune response. The authors advocate for the systematic inclusion of pets in health monitoring systems during pandemics, in order to better understand the dynamics of cross-species transmission.