New medical data shows that a new strain of the coronavirus can be transmitted from dogs to people.
It has long been known that humans can contract viruses from animals, with different coronaviruses, including SARS, jumping from civets to humans — but instances of transmission of the canine coronavirus to people had never been recorded before.
The coronavirus itself is not rare in the world and it raises its ugly head fairly often around the globe. MERS, the Middle Eastern variant, emerged from camels and spread to people ten years ago.
Dr. Gregory Gray, of Duke University’s Global Health Institute, speculated at the outbreak of the Covid-19 pandemic in 2019 that there possibly were other types of coronavirus in the world that posed a threat to the globe.
Current coronavirus tests don’t account for many strains of the virus
He was stymied, however, by the fact that the test used to detect Covid-19 was limited, in that it only shows whether or not one type of coronavirus — SARS-CoV-2 — is present, and no other form of the virus.
In a recent NPR report Gray, an infection disease epidemiologist, explained the issue he faced, saying “Diagnostics are very specific. They generally focus on known viruses.”
He then asked one of his colleagues, graduate student Leshan Xiu, to create a more powerful test that would show the presence of all types of coronaviruses -even those that had been unknown up until now.
The tool Xiu created worked even better than Gray had expected, opening a new world into the battle against the coronavirus.
In only their first round of samples that they tested, Gray and Xiu discovered evidence of an entirely new coronavirus that is now linked to pneumonia in hospitalized patients, mostly in children.
New strain of the coronavirus linked to canines
On Thursday, the Journal of Clinical Infections Diseases published the results of their groundbreaking work, which showed that the coronavirus raging across the world this past year could be the eighth coronavirus known to infect humans.
National Public Radio (NPR) states that the patients who provided the samples used in the study were from a hospital in Sarawak, Malaysia; the deep nasal swabs used — just like those used on people today to test for the coronavirus — were collected in 2017 and 2018.
Thought at the time to all have been suffering from pneumonia, a surprising eight out of the 301 individuals tested were found to have been infected with a new canine coronavirus.
This 2.7% infection rate with a previously completely unknown virus was very unusual, According to Gray, who told reporters “That’s a pretty high prevalence of a (new) virus,” Gray says. “That’s remarkable.”
The ending was so very unusual that he though he and his young colleague must have made an error. “You always wonder if there was a problem in the lab,” he says.
Just to make sure all was indeed as he was seeing it, Gray sent the samples to Ohio State University, to a renowned expert in the field of animal coronaviruses.
Ever the careful researcher, she too thought something had to be amiss.
Virologist Anastasia Vlasova admits “I thought, ‘There’s something wrong. Canine coronaviruses were not thought to be transmitted to people. It’s never been reported before.”
It was then that Vlasova set to work to try to understand the unprecedented findings. When she attempted to grow the new type of coronavirus in the lab, employing a special solution that had in the past worked for other dog coronaviruses, she found that “the virus grew very well,” she recalls.
Fortunately, with these many samples to work with , the researcher discovered that she could even determine its entire genome. Looking at the gene sequences of the virus, Vlasova could see that it had likely infected cats — and even pigs — at one point in its past.
However, the most remarkable finding of all is that it had traversed directly from dogs into people. As she explains, “The majority of the genome was canine coronavirus.”
Viral deletion allowed canine strain to spread to humans
She noticed with alarm that there was yet another unusual aspect of the virus. “We did discover a very, very unique mutation — or deletion — in the genome.”
This deletion is not present in any other known canine coronaviruses; however, it is found in human coronaviruses.
“It’s a mutation that’s very similar to one previously found in the SARS coronavirus and in (versions of) SARS-CoV-2 … (that appeared) very soon after its introduction into the human population,” Vlasova points out.
It is this very deletion, in her opinion, that enables the canine virus to infect humans. Moreover, it may be the key step that is required for coronaviruses to cross over the interspecies border into humans.
This enormous scientific discovery may enable researchers to figure out how to fight this particular type of coronavirus before it adapts itself further by mutation — as all viruses do — and spreads as part of another outbreak.
No evidence of transmission from human to human
So far, scientist have not found that the virus has indeed jumped from humans humans yet, however. Virologist Xumin Zhang at University of Arkansas for Medical Sciences states “There’s no evidence yet of transmission from human to human.”
However, it is still unknown at present exactly how the Malaysian patients became infected with the virus — including even whether they had direct contact with infected animals or not.
Zhang, who has devoted more than 30 years of his career to the study of coronaviruses, thinks it is too early to declare this new virus a human pathogen.
“As the authors are careful to say in their paper, they have not proven what’s called Koch’s postulates,” he explained to NPR. To laymen, that means Vlasova, Gray and their colleagues have not actually shown that the new canine coronavirus causes pneumonia. Thus far, it has only been “associated with” the disease.
And that point may be far into the future because of how this causation would have to be scientifically proven. “To do that, strictly, they need to inject the virus into humans and see if it reproduces the disease,” Zhang says.
“Of course (for ethical reasons), we cannot do that,” he explains.
But all is not lost in this major breakthrough since scientists all over the globe can check to see how common the virus is in patients suffering from pneumonia. In addition, of course, they can also conduct experiments in mice or other animals.
Zhang tells reporters that he would not be surprised if this new virus is “a new human pathogen,” adding that the more scientists look for such new coronaviruses in those suffering from pneumonia, the more they will discover. “I believe there are many animal (coronaviruses) out there that can transmit to humans,” he states.
They way to defeat further interspecies jumps of coronaviruses, he says, is to test more people in order to track down these unusual infections — before they can pose yet another problem for the health of the world.