A New Canine Coronavirus That Can Be Transmitted to Humans

American and Asian researchers have isolated a new coronavirus of canine origin in patients with pneumonia in Malaysia. It is potentially the eighth coronavirus to have crossed the species barrier to infect humans. However, for now, this recombinant canine coronavirus does not pose a pandemic risk.    Scientists recently announced the discovery of a new coronavirus that can be transmitted from dogs to humans . The virus was discovered in a young patient with pneumonia in Malaysia. The case dates back to 2018, but the virus was only recently identified. Nasopharyngeal samples from 300 patients hospitalized that year for pneumonia in Sarawak were screened. In eight of them—including seven children—researchers found traces of a canine coronavirus, and in the young patient in question, the isolated virus was found to be capable of causing an infection in vitro in the presence of these canine cells. It appears to be a new alphacoronavirus, dubbed CCoV-HuPn-2018. As the first canine coronavirus detected in humans, it adds to the list of coronaviruses that are pathogenic to humans. However, it remains to be demonstrated that this new virus is actually the cause of the pneumonia observed in the eight infected children. In total, seven other coronaviruses cause diseases of varying severity in humans. The alphacoronaviruses HCoV-229E and HCoV-NL63 cause mild colds, as do the betacoronaviruses HCoV-OC43 and HCoV-HKU1. In contrast, SARS-CoV, MERS-CoV, and the well-known SARS-CoV-2 are much more virulent beta-coronaviruses. Most are closely related to strains isolated from bats, which serve as a major reservoir for coronaviruses. It is therefore surprising that the latest virus discovered by researchers is a canine enteric coronavirus (CCoV), which normally affects only dogs, causing vomiting, fever, and diarrhea. “We initially thought it was an external source of infection ,” Gregory Gray, an infectious disease specialist at Duke University and co-author of the study, told The New York Times . In fact, there is no direct evidence to conclude that the virus was transmitted to humans by dogs. But according to sequencing, this is the most likely route of transmission. There is also the possibility that an intermediate host was involved—likely a cat. Indeed, CCoV-HuPn-2018 resulted from a recombination of two strains of canine coronaviruses, along with fragments of feline and swine coronaviruses. Sequencing of the virus also revealed a characteristic specific to the canine virus: it contains a deleterious mutation that is absent from all other canine coronaviruses but present in human coronaviruses. This 36-nt (12-aa) deletion causes dramatic changes in the virus’s cellular localization shortly after its zoonotic transmission. The mutation helps the canine virus persist within the human body and could be a necessary step in its transmission to humans. It is found in particular in the coronaviruses responsible for severe acute respiratory syndrome (SARS and SARS-CoV-2). For now, the new recombinant canine coronavirus is not a cause for concern. To date, there is no evidence that it is transmissible from person to person, nor even that it is actually the cause of the observed pneumonia. However, it highlights the vulnerability of human populations to the emergence of new pathogens, whether through contact with wildlife or domestic animals. “It is likely that many animal viruses coexist in both humans and animals, but we have never detected them ,” confirms Xuming Zhang, a virologist at the University of Arkansas. Nevertheless, it is impossible to monitor them all. In April 2021, researchers did, however, rank the known animal viruses most likely to be zoonotic. But that won’t prevent the next pandemic threat from originating from completely unknown strains...