S.Scientists have identified two new coronaviruses in humans, but they have not been shown to cause disease or spread to other people. One study identified pigs as the animal hosts of a virus, and another study found that a coronavirus likely came from dogs. For the first time, a canine coronavirus has been shown to infect humans.
“This research clearly shows that more studies are urgently needed to assess critical questions about the frequency of cross-species [coronavirus] Transmission and potential for human-to-human spread, ”reports Ralph Baric, a virologist at the University of North Carolina at Chapel Hill who was not involved in either study science.
The dog study, published May 20 in Clinical Infectious DiseasesGregory Gray, an infectious disease epidemiologist at Duke University, had reported at the start of the pandemic NPR. He wondered if there were already other coronaviruses infecting people that might one day trigger outbreaks and asked his graduate student, co-author Leshan Xiu, to design a test that would not only detect SARS-CoV-2 but so far would detect unknown coronaviruses.
The team used their diagnostic test to examine more than 300 nasal swabs from pneumonia patients in Borneo, Malaysia in 2018. Eight patients, or 2.7 percent, had evidence of previous exposure to a novel coronavirus, and seven were children. science Reports. For a previously undetected virus, “that’s a pretty high prevalence,” says Gray NPR. “That is remarkable.”
Gray sent samples of the virus to Anastasia Vlasova, an animal coronavirus expert at Ohio State University, and she found that the virus was actually a chimera – parts of its genome matched a feline coronavirus while another part matched a pig -Coronavirus was similar. However, most of its genome was most similar to two coronaviruses previously isolated from dogs, and she was able to grow the virus in dog cell cultures. “It was not believed that coronaviruses could be transmitted to humans in dogs,” says Vlasova NPR. “It has never been reported.”
It is not clear whether the virus known as CCoV-HuPn-2018 caused the patient’s pneumonia, and it is not yet known whether the virus is able to jump from person to person or react like an adult immune system could if it were. “We currently have no real evidence that this virus can cause serious illness in adults,” Vlasova said in a press release.
She found that the virus had a key mutation – a deletion – that was not found in other canine coronaviruses, but in those that infect humans. While further research is needed to determine whether this mutation is required to initiate a cross-species jump, Vlasova adds that she “cannot rule out the possibility that this new coronavirus will eventually become a widespread human pathogen. As soon as a coronavirus can infect a human, all bets are void. “
Speak with NPRXumin Zhang, a virologist at the University of Arkansas Medical Sciences, says, “As the authors carefully point out in their paper, they have not proven what is called Koch’s postulates.” This means that in order to infect a person with the virus, they would have to to show that it causes pneumonia. Such an experiment would be unethical, he adds, but they could instead test more samples to see how common the virus is in pneumonia patients and then use animal models to test their hypotheses.
The pig study, published as a preprint on medRxiv In March, a new coronavirus was identified in serum samples from three Haitian children who were hospitalized with a fever between 2014 and 2015. Researchers at the University of Florida were able to grow the virus in monkey cells and genome analysis showed it was very close to known delta coronaviruses in pigs.
Coronaviruses can be divided into four groups: Alpha, Beta, Gamma and Delta. It used to be believed that delta coronaviruses only infected birds. science Reports. But in 2012 one appeared on pigs in Hong Kong believed to have jumped from songbirds. The same virus caused an outbreak in pigs in the US in 2014, and delta coronaviruses have since been shown to infect human cells as well.
The most dangerous coronaviruses for humans – SARS-CoV, SARS-CoV-2 and MERS-CoV – were all betas. While delta coronaviruses cause significant outbreaks in animals, it hasn’t in humans. Alphas, including the canine coronavirus isolated in Malaysia, have never caused epidemics in humans either, says Texas A&M University virologist Benjamin Neuman science“But that doesn’t feel like much comfort in the wild world of viruses.”
Taken together, the studies suggest that coronaviruses are likely to circulate more frequently in animals than previously thought. “I think the more we look, the more we will find that these coronaviruses are crossing species everywhere,” says Stanley Perlman, virologist of the University of Iowa, who was not involved in the work science.
According to Gray in the press release, the goal is to detect these viruses before they cause disease in humans. “We are probably missing key animal viruses that are gradually adapting to humans,” he says, adding that places where animals and humans mix, such as open markets or farms, could be good places to look for “early warning.” search[s] a new virus that may become a future pandemic virus. ”