A group of reputable international scientists have announced that they have identified a new canine coronavirus. Their results were published in the specialized journal Clinical Infectious Diseases. We learn in particular that this new coronavirus was discovered in samples taken from patients hospitalized for pneumonia in a hospital in Sarawak, a state of Malaysia located on the island of Borneo (in 2018, editor’s note).
This discovery may seem alarming: could dogs transmit dangerous coronaviruses to us? Don’t panic: we will quickly find that there is no reason to worry.
What do we know about this canine coronavirus? First important information: it differs a lot from the SARS-CoV-2 coronavirus which is the cause of the Covid-19 pandemic. The coronavirus family can in fact be divided into four groups: alpha, beta, gamma and delta coronaviruses. Canine coronaviruses are part of the alpha-coronavirus group, while SARS-CoV-2 is part of the beta-coronavirus group. These two groups are totally distinct.
Scientists know the existence of canine coronaviruses for almost 50 years. These viruses were of primary interest only to veterinary virologists and, occasionally, dog owners. Until now, there has been no record establishing that these coronaviruses could infect humans. But that doesn’t mean they didn’t; the current situation, by shining the spotlight on coronaviruses, now leads us to discover them in places where we had never looked for them until now.
Canine coronavirus infections demonstrated in humans, the discovery of which was reported in Clinical Infectious Diseases, were incidentally identified. The patients from which the samples were taken had long been cured of their pneumonia, and scientists were not specifically looking for canine coronavirus in the samples available to them. They were working to develop a new test to simultaneously detect all types of coronavirus (test which they dubbed pan-CoV).
After developing their protocol and confirming that it worked on virus samples grown in the lab, the researchers used it to test 192 human samples, which had been taken by swab from hospital patients with pneumonia in Malaysia. Nine of these samples tested positive for coronavirus.
Evgeniy Kalinovskiy/Alamy
Further analysis showed that five of those nine samples contained ordinary human coronaviruses, which can cause colds. But, surprisingly, four samples contained canine coronaviruses. Further study of patient samples from the same hospital revealed that four additional samples were also positive for these canine coronaviruses.
The researchers then studied swabs from the nose and throat of these eight patients in an attempt to learn more about the canine coronaviruses they contained. In their lab, they placed the samples in contact with dog cell cultures to see if any infectious viruses were still there. The experiment was only conclusive with only one of these samples: the viruses it contained actually replicated, and viral particles could be observed under an electron microscope. Scientists have also been able to sequence the genome of this virus.
Analysis of the data showed that this canine coronavirus is closely related to a few different alpha-coronaviruses, some of which infect pigs and cats. She also revealed that this coronavirus had never been identified elsewhere.
No evidence of dissemination
Was this canine coronavirus the cause of the pneumonia of the eight patients? At present, it is impossible to say. Seven of the eight patients were in fact simultaneously infected with various other viruses when they developed the disease: adenovirus, influenza virus (influenza) or parainfluenza virus. We know that all of these viruses are capable of causing pneumonia on their own, so it is more likely that the disease was caused by them rather than that of the canine coronavirus. At most we can say that there is an association, in these patients, between the fact of declaring pneumonia and the presence of the canine coronavirus, but we cannot affirm that there is a causal link.
Fears have been expressed that the canine coronavirus identified in these patients could be transmitted from person to person, and thereby trigger an epidemic outbreak. But what the newspaper headlines did not specifyis that these infections actually occurred in 2017 and 2018. No such spread has been detected in recent years, which further weakens the likelihood that this virus could be the cause of infectious foci.
Our attention is now focused on coronaviruses. We will inevitably find more and more of them, in unexpected places, as we continue our research to identify viruses that are related to them. The vast majority of them will only be of interest to the researchers who study them, and should not worry us. However, it is essential that coronavirus surveillance continues and is expanded, so that we can maximize our chances of identifying problematic species jumps that could occur in the future at an early stage.
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