These viruses go under the radar but could already be circulating around you
Since the beginning of the year, American virologists have been sounding the alarm on two infectious agents until now almost unknown to the general public. These viruses of animal origin are already spreading widely in their hosts and are showing signs of passing into humans, in a global context still marked by the Covid-19 pandemic.
In a review article published in January in the journal
Emerging Infectious Diseasesteams from the University of Florida and the University of Texas estimate that the
influenza D virus and the canine coronavirus could become the next big threats to public health if surveillance remains insufficient. What do they know about these viruses that we almost never talk about?
Influenza D: a livestock virus that discreetly approaches humans
Identified in 2011 in pigs suffering from respiratory disorders, influenza D virus mainly infects cattle, but also other animals such as poultry, deer, giraffes or kangaroos. It contributes to bovine respiratory disease, which is estimated to cost the US livestock industry approximately $1 billion per year.
In humans, several studies in Colorado and Florida have shown that up to 97% of workers in contact with herds carry antibodies against this virus, a sign of repeated exposure but without symptoms, so-called subclinical infections. In China, a recent strain, D/HY11, was transmitted by air between ferrets and replicated well in human airway cells, suggesting an emerging capacity for person-to-person transmission.
Canine coronavirus HuPn‑2018: from dogs to human pneumonia
THE canine coronavirus HuPn‑2018a recombinant alphacoronavirus from canine, feline and porcine viruses, is not the SARS-CoV-2 responsible for Covid-19. It causes diarrhea in dogs, but it has mainly been isolated from a child hospitalized for pneumonia in Malaysia. An almost identical strain, called HuCCoV_Z19Haiti, was found in a medical team member returning from Haiti with moderate fever and malaise.
Very similar viruses were then detected in patients suffering from respiratory infections in Thailand, Vietnam and the state of Arkansas, a sign that they are already circulating on several continents. In Hanoi, this coronavirus was spotted in 18 out of 200 patients hospitalized for pneumonia. Additional problem: it escapes routine respiratory test panels, which makes it almost invisible in emergency departments.
Why these two viruses worry researchers
“To date, influenza D virus has not been associated with serious infections in humans.”said John Lednicky, research professor at the University of Florida and member of the University of Florida Institute for Emerging Pathogens. “However, canine coronavirus has been associated with serious infections, but diagnostic testing is not routinely performed for this virus, so the extent of its impact on the general population remains unknown.”.
Scientists’ concern is linked to an explosive cocktail: large animal reservoirs, already frequent human exposures and the total absence of dedicated commercial PCR or serological tests.
“Our analysis of the scientific literature indicates that these two viruses pose a threat to human respiratory health, yet few measures have been taken to contain or prevent infection.” said John Lednicky.
“If these viruses evolve the ability to spread easily from person to person, they may be capable of causing epidemics or pandemics since most people will not have immunity to them.”.
They continue by calling for strengthening surveillance at human-animal interfaces, developing targeted tests, evaluating antiviral treatments and, if the risk is confirmed, considering human vaccines against these new respiratory viruses.
“Our knowledge of the epidemiology and clinical manifestations of viruses is limited to a modest number of research studies (…) Even so, limited data regarding these newly detected viruses indicate that they pose a major threat to public health“.
Currently, no coordinated strategies are in place to detect or contain these emerging infectious agents. A delay that virologists consider worrying, in a world where pandemics are no longer the exception but a recurring risk.