Early in 2017, a team of medical personnel, including doctors, nurses and volunteers, returned home to Florida after volunteering at a clinic in Haiti. Soon after their return, 20 members of the team began to feel a bit under the weather.
"They had a slight fever and didn't feel 100% right," says virologist John Lednicky at the University of Florida. "But they weren't very sick."
At the time, Zika virus was circulating in Haiti, and health officials were worried the travelers might have been infected, potentially importing the mosquito-borne illness to Florida. So officials took urine samples from each traveler and asked Lednicky to test for Zika.
Lednicky ran the standard PCR tests for the virus, and they all came back negative. But he wasn't satisfied. He had a hunch that the urine samples did contain a virus — not Zika but something else.
So he took a little bit of the urine from six of the travelers and added it to a special solution of monkey cells. The goal was deceptively simple: to see if any viruses in the urine would infect the monkey cells, start replicating and grow to detectable levels. Then Lednicky could collect the virus's genes and identify it.
"This is what we do in our lab," Lednicky says. "We cast a wide net. We try to isolate viruses. And oftentimes, when we do that, the unexpected happens."
Indeed, the unexpected occurred.
"We found a coronavirus," he says. And not just any coronavirus, but one that many scientists believe may be a new human pathogen — likely the eighth coronavirus known to cause disease in people. Turns out, this coronavirus in the Haiti travelers has cropped up previously, on the other side of the globe.
Coronavirus from dogs likely causes pneumonia in kids
Back in May, scientists at Duke University reported they had detected a nearly identical virus coronavirus in children at a Malaysian hospital.
The researchers found the virus in the upper respiratory tract of 3% of the 301 patients they tested in 2017 and 2018.
The genetic sequence of the Malaysian virus suggested it likely originated in dogs and then jumped into people. "The majority of the genome was canine coronavirus," virologist Anastasia Vlasova told NPR in May.
Although the findings sounded alarming, the researchers had no evidence that the virus could spread among people or that it was widespread around the world.
"These human infections with ... canine coronaviruses appear to be isolated incidents which did not lead to extensive human transmission," virologist Vincent Racaniello wrote on the Virology Blog.
Now Lednicky and his colleagues have found an almost identical virus infecting people 11,000 miles away — at the same time. The genetic sequence of the virus in Haiti is 99.4% identical to the one in Malaysia. Lednicky and his colleagues reported this past Sunday in the journal Clinical Infectious Diseases.
And the big question is: How does a dog virus in Malaysia wind up in doctors and nurses in Haiti?
A widespread virus, but how it spreads is a mystery
"The virus probably circulates widely, but no one has paid attention to it," Lednicky says. He suspects it's all over the world. And if you've been around dogs frequently, you might have been infected with this virus — or developed an immunity to it by exposure to similar virus. "We'll know when scientists start looking for antibodies inside older blood samples taken from patients with respiratory disease. How many of them were misdiagnosed all along?"
Some scientists also think doctors and researchers should start actively looking for this virus in patients. "I think that's important for several reasons," says virologist Linda Saif at Ohio State University, who has studied coronaviruses for about 40 years.
"No. 1, this virus has been associated with a number of pneumonia cases in children, and No. 2, we really don't know if it can transmit from human to human," she adds.
The fact that scientists detected the almost-identical viruses in both Haiti and Malaysia, at the same time, suggests the virus does spread among people, Saif says.
"There's a temporal sequence here. These two viruses — which are very, very similar — have been detected in a similar time frame but in widely separated regions of the world," she explains. That could happen if a nearly-identical virus was circulating in dogs in both Haiti and Malaysia and then jumped over to people in both countries during the same year.
"I would be very surprised if that happened," Saif says.
The second hypothesis is that the virus is circulating in people, at low levels, in many parts of the world, under the radar. "That hypothesis is more likely," Saif says.
If that hypothesis turns out to be true, this canine coronavirus will be the eighth coronavirus known to spread among humans.
Why this finding is good news
On the surface, these new findings sound like horrible news. The last thing the world needs right now is another coronavirus — one that may trigger pneumonia in children. But Jonna Mazet says it's actually good news because it means scientists have caught this virus before it has caused a big problem.
"The very exciting part is that people are starting to do virus discovery and characterization, even when large groups of people aren't dying and or getting severely ill, which is how most virus discovery has happened in the past," says Mazet, who's an epidemiologist at the University of California, Davis and the founding executive director of the One Health Institute there.
By finding this virus early, scientists now have time to study it, create tools to diagnose it and understand what it might take to stop it. Although it's not a cause for deep concern at this time, there's always the risk the virus could evolve and become a bigger problem, Mazet says, as was likely the case with SARS-CoV-2, which causes COVID-19.
"Almost certainly, SARS-CoV-2 was circulating for quite some time and making people either a tiny bit sick or not sick enough to be noticed," she says. If scientists had detected it at this stage, perhaps the world would have had time to develop a test for it, some promising treatments and even a preliminary vaccine. Perhaps the pandemic would have taken a much different — perhaps less deadly course.
"We need to find these novel viruses well before they fully adapt to humans and become a pandemic problem," writes epidemiologist Gregory Gray, from the University of Texas Medical Branch, in an email to NPR. "Fortunately, today we have the tools to both detect and evaluate the risk of such novel viruses. We just need the political will and financial support to do so."