Recent reports suggest that a dog in the U.S. has tested positive for the novel coronavirus that causes COVID-19. Winston, a pug, and the humans in his family tested positive. The family noted that Winston “wasn’t tested because they thought he was sick,” but as part of a research project at Duke University.
Winston is the first dog in the U.S. reported to test positive and the third in the world (two in Hong Kong), but there is reason for healthy skepticism. And none of the evidence suggests there is reason to worry about your dogs or yourself. Why?
First, the two dogs in Hong Kong do not appear to have been truly positive. The “weak positive” test on the first dog was followed by a negative test result from rectal swab and fecal sample. The “weak positive” result, according to the American Veterinary Medical Association moreover, “does not distinguish between RNA detected from intact virus and that detected from fragments of viral RNA;” the latter of which has not resulted in an infection. Although there were further “weak positive” results with follow up testing, ultimately “Virus isolation was performed with negative results.” Unsurprisingly, the dog did not show any symptoms.
The second dog had positive results on one test and then negative results on a confirmatory test. The other dog living in the same house tested negative both times. “Neither dog has shown signs of respiratory disease“.
Second, a positive result in Winston has not been confirmed by the U.S. Department of Agriculture via the testing of additional samples. Neither the USDA nor the AVMA have updated their websites to confirm a positive result in the dog.
Third, a study which tried to deliberately infect dogs with SARS-CoV-2, the virus which causes COVID-19, found that none of the dogs acquired it, despite being injected with a massive dose directly up their noses (over 30 times greater than would be found in nature).* Although some of the dogs initially tested positive by rectal swab, the tests are not foolproof. All the dogs were ultimately found to be negative upon tissue analysis. Ultimately, the study concluded that dogs are not susceptible to COVID-19.
Fourth, even if Winston is truly positive, it would be rare — so rare, in fact, that given the ambiguity around the two dogs in Hong Kong, he would be the first truly positive case in the world. Dr. Jane Sykes, the Chief Veterinary Medical Officer of the UC Davis Veterinary Medical Teaching Hospital, noted that, “There are major diagnostic laboratories in the U.S. that have now tested more than 6,000 dogs and cats, from all over this country [and] from other impacted countries since the outbreak began and all of those animals have tested negative”.
In fact, Idexx Laboratories has analyzed more than 5,000 samples “from pet cats and dogs in 17 countries that were submitted by veterinarians for respiratory-related tests. It found zero cases…” Another commercial laboratory in the United States also reported they had tested “thousands of specimens from dogs and cats for SARS-CoV-2 and had obtained no positive results. These specimens have come from the United States, South Korea, Canada, and Europe, including regions concurrently experiencing human COVID-19 cases”. By contrast, over three million humans have tested positive and over 230,000 have died. So regardless of whether dogs are susceptible to COVID-19, the chance of infection would likely be infinitesimally low.
Fifth, if dogs could acquire it — and that is a big if — they are almost certainly “dead end hosts” and as such, cannot pass it to other animals or to people. According to a Tufts University virologist, “The virus may be able to infect tissues or cells in a host, say, the respiratory tract, but they’re not able to complete the life cycle in terms of transmitting to a new host“. In fact, another dog and a cat in the same household as Winston tested negative (the bearded dragon that rounds out their family was not tested).
To date, the U.S. Department of Agriculture says that, “there is no evidence that pets play a role in spreading the virus in the United States. Therefore, there is no justification in taking measures against companion animals that may compromise their welfare”.
Likewise, “The CDC, the World Health Organization, the World Organization for Animal Health and other public health bodies and experts agree on this: There’s no evidence that animals transmit the virus to humans or have played a role in its spread“.
In sum, the AVMA admonition continues to hold true that dogs “are not readily infected with SARS-CoV-2, we have little to no evidence that they become ill, and no evidence that those that may be naturally infected spread SARS-CoV-2 to other pets or people.” As such, there is nothing in the dramatic headlines about Winston that warrant fearing, quarantining, or staying away from our dogs.
* It should go without saying that there are ethical issues inherent in any study that would deliberately attempt to inflict on sentient, non-human animals a disease so grave in terms of potential suffering and death that we have all collectively adopted extreme measures, including shutting down the economies of the world, to avoid contracting it ourselves.
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