PETS DO NOT APPEAR TO BE EASILY INFECTED WITH SARS-COV-2
During the first five months of the COVID-19 outbreak (January 1 – June 8, 2020), which includes the first twelve weeks following the March 11 declaration by the WHO of a global pandemic, fewer than 20 pets have tested positive, with confirmation, for SARS-CoV-2 globally. This despite the fact that as of June 8, the number of people confirmed with COVID-19 exceeded 7 million globally and 1.9 million in the United States.
have been fewer than 25 reports from around the world of pets (dogs and cats) being infected with SARS-CoV-2; however, none of these reports suggest that pets are a source of infection for people. Evidence to date from the few domestic animals that have tested positive for SARS-CoV-2 indicate these infections are typically a result of close contact with people with COVID-19. In laboratory studies of experimental infection with SARS-CoV-2, ferrets, Syrian hamsters, and cats—all animals that may be kept as pets—show potential for serving as animal models of human infection, but dogs, pigs, chickens, and ducks do not. And, although molecular modeling and in vitro studies suggest that multiple animal species may theoretically be able to be infected with SARS-CoV-2, a definitive intermediate host has not been identified. There is little to no evidence that domestic animals are easily infected with SARS-CoV-2 under natural conditions and no evidence to date that they transmit the virus to people. The primary mode of transmission of COVID-19 in humans is person-to-person spread.
Additional evidence that pets appear to be only rarely infected with SARS-CoV-2 under natural conditions comes from two commercial laboratories in the United States, which in April 2020 announced the availability of a reverse transcriptase polymerase chain reaction (RT-PCR) test for SARS-CoV-2 in domestic animals, including cats and dogs. During development and validation of these tests, each laboratory assessed thousands of specimens from dogs and cats for the COVID-19 virus without obtaining any positive results. Those specimens came from pets located in the United States, South Korea, Canada, and Europe, including regions that were concurrently experiencing a high number of human COVID-19 cases. While this is encouraging, the specimens tested were originally submitted for PCR analysis of more common pathogens that cause respiratory disease in dogs and cats and, as such, per-case information as to whether these pets had contact with suspected or confirmed COVID-19 positive people is not available.
The first confirmed reports of pets infected with SARS-CoV-2 came from Hong Kong. Since the onset of the outbreak there, government officials with the Agriculture, Fisheries, and Conservation Department (AFCD) recommended that mammalian pets from households with persons hospitalized because of COVID-19 be cared for in quarantine and tested for infection with SARS-CoV-2. As of April 15, 30 dogs, 17 cats, and two hamsters had been held at the AFCD quarantine facility. However, only two dogs and one cat have tested positive for SARS-CoV-2 infection. Infection was confirmed by detection and sequencing of viral RNA in upper respiratory tract samples and detection of neutralizing antibodies against the virus in serum. Virus also was isolated from one of the two infected dogs. None of the animals in quarantine, including the three positive pets, developed clinical signs of respiratory disease and all positive animals were released from quarantine after at least a 14-day stay and negative RT-PCR test results on samples collected over at least two consecutive days. On May 14, an article describing SARS-CoV-2 infection in the two Hong Kong dogs was published online in Nature.
The first reports of positive pets in the United States came on April 22 when the CDC and National Veterinary Services Laboratories (NVSL) reported that two cats in New York state were confirmed to be infected with SARS-CoV-2. Both cats had signs of mild respiratory illness and were expected to make a full recovery. The owner of one of these cats was confirmed to have had COVID-19; a second cat living in this same household tested negative for the virus. The second positive cat was an indoor-outdoor cat whose owner had no symptoms of COVID-19 and was never tested. However, it lived in an area with a high number of human COVID-19 cases. It was presumed that that this cat was infected by either its owner, who was asymptomatically infected with SARS-CoV-2, or by another infected person in the neighborhood. A case report describing clinical signs and progression in these two cats and diagnostic tests completed was published in the June 8, 2020 issue of the Morbidity and Mortality Weekly Report. Until June 1, these are the only two positive pets confirmed to be infected in the United States.
On June 2, the USDA NVSL announced the first confirmed case of SARS-CoV-2 in a dog in the United States. This pet, a German Shepherd Dog, lived with one other dog and their two owners in New York state. One of the dogs’ owners had tested positive for, and the second had symptoms consistent with, COVID-19 prior to the German Shepherd Dog developing signs of respiratory illness. The second dog in the household remained apparently healthy. Samples taken from the affected German Shepherd Dog tested presumptive positive for SARS-CoV-2 by use of RT-PCR performed at a private veterinary laboratory, which then reported its results to state and federal officials. Results of further laboratory tests performed at the NVSL on the original and additional samples collected from the German Shepherd Dog confirmed that this dog was infected with SARS-CoV-2. The dog was presumed to have been infected by its owners and is expected to make a full recovery. Results of serological tests conducted by the NVSL on the second dog in the household revealed virus-specific antibodies, indicating that although this dog never developed clinical signs of disease, it had been exposed to the COVID-19 virus.
An in-depth summary of these and other reported cases of naturally occurring SARS-CoV-2 infection in animals is available for those who wish to learn more. It will be updated regularly, so we encourage you to check back often.