#16,944
When a zoonotic virus like COVID, MERS-CoV, Avian flu, or Monkeypox jumps species into humans - and begins to spread globally - there are always concerns that the virus will spill back into the animal population, either in new locations or even into previously unaffected species.
With COVID, we've already seen this happen in farmed mink and in wild deer, and to a lesser extent, companion animals (dogs and cats). Not only could this add another reservoir host for the virus, it can lead to the emergence of new, potentially dangerous, mutations.
In late 2020, Danish authorities announced the spillover of COVID into millions of susceptible farmed mink, and the discovery of several `mink specific' mutations in the virus (see Denmark Orders Culling Of All Mink Following Discovery Of Mutated Coronavirus), which subsequently jumped back into the human population.
Danish authorities immediately ordered a full 4 week lockdown, and emergency testing of all residents in North Jutland, where the virus had emerged. For several weeks, numerous countries enacted travel bans on Denmark.
The crisis was short-lived, as this `mink variant' died out when a newer, more `biologically fit' Alpha Variant emerged in the UK, and began to spread globally.
Since early 2021 we've seen numerous reports of SARS-COV-2 spillover into North American White-Tailed Deer (see USDA/APHIS: White-Tailed Deer Exposed To SARS-CoV-2 Detected In 4 States).
Last February, in Preprint: Evolutionary Trajectories of SARS-CoV-2 Alpha and Delta Variants in White-Tailed Deer in Pennsylvania, we looked at evidence of the generation of deer-derived alpha variants that "diverged significantly from those in humans"
A year ago, Chinese scientists warned that `reverse-zoonosis' could lead to the emergence of new COVID variants - and even coronavirus recombinants - that could threaten humans for years to come (see CCDC Weekly Perspectives: COVID-19 Expands Its Territories from Humans to Animals).
Concerns that have also been voiced by others in the international community (see WHO/FAO/OIE Joint Statement On Monitoring SARS-CoV-2 In Wildlife & Preventing Formation of Reservoirs).
We've routinely seen humanized influenza viruses (H1N1, H3N2) spill back into swine, and continue to evolve, as well as infecting dogs, cats, and marine mammals. Occasionally, we see a spillover of one of these `variant' viruses back into humans, reminding us that what goes around, comes around.
Many of these same concerns apply to Monkeypox, which is being efficiently spread around the globe by humans, and has the potential for spilling back into other species.While the Monkeypox Virus (MKPV) doesn't spread as readily as a respiratory virus (like COVID or influenza), we've seen evidence (see EID Journal: Environmental Persistence of Monkeypox Virus on Surfaces in A Household) that once shed, the virus can remain viable on porous surfaces (like towels, bedclothes, clothing, etc.) for days.
Last week The Lancet carried a correspondence from France detailing what appears to be the first human-to-dog transmission of MKPV in a household setting (see below), raising new concerns that the virus could spread to local non-human species.
Evidence of human-to-dog transmission of monkeypox virus
The Lancet Published: August 10, 2022Sophie Seang, Sonia Burrel, Eve Todesco, Valentin Leducq, Gentiane Monsel, Diane Le Pluart, and others
Which brings us to the following statement from the World Organisation for Animal Health (WOAH).
Remaining on alert: how monkeypox could spread back to animals from humans
Published on 12 August 2022
While the monkeypox outbreak continues to spread amongst humans, the World Organisation for Animal Health (WOAH, founded as OIE) explains the precautions to take in order to protect animals from the increase in reverse spillover of the disease back into animals.
Monkeypox has become the star of recent health news, affecting over 16,000 people in at least 75 countries around the world. Like many other diseases, such as COVID-19 which affected 23 different animal species, monkeypox could cross the species barrier and jump to domestic and wild animals, putting everyone’s health at risk. At the World Organisation for Animal Health, our mission is to improve animal health globally. As monkeypox endangers us all, we must insist on why and how precautions should be taken to reduce the risk of transmission to animals.
Although the current outbreak of monkeypox is driven by human-to-human contact, the disease is known to be of animal origin and can therefore be passed on to certain species. Various wild mammals have been identified as susceptible to the monkeypox virus, such as rope squirrels, tree squirrels, Gambian pouched rats, dormice and non-human primates. While some of these species exhibit signs and symptoms of the disease, others might not show any external or visible signs, which makes it more challenging to identify spillover events.
Very recently, monkeypox was detected in a dog most likely as a result of human to animal transmission following close direct contact with its owners who were symptomatic with the disease. This was the first documented case of human to animal transmission of the virus. We must remain vigilant. In case of further spillback of the virus from infected humans to animals, new animal reservoirs could be established, and the virus could become endemic in new geographic areas, heightening future risks for public health as well.
The World Organisation for Animal Health is closely monitoring the situation, in coordination with its experts because the heightened prevalence in humans may increase the risk of transmission to animals, and affect the epidemiology of the disease.
Dr Monique Eloit, Director General at the World Organisation for Animal Health
A few (and simple!) precautions must therefore be taken. Always ensure that all waste, including medical waste, is safely disposed of and made inaccessible to rodent or other scavenger animals. And, if you are suspected or confirmed to be infected with the monkeypox virus, you should avoid all direct contact with animals, including livestock, wildlife, and even your pets.We all need to be cautious. Monkeypox is yet another example of how human and animal health are interconnected. Only with strong multi-sectoral collaboration between public health experts, veterinarians, and wildlife authorities can we tackle diseases such as monkeypox, and ensure a safe future for us all.
Viral transmission from humans to animals is a possibility that we need to further investigate to understand how likely this is to happen. All settings where we interact closely with animals, like zoos, wildlife rehabilitation facilities, hiking trails or at home with our pets, can facilitate the virus jumping from us to them. The monkeypox virus can enter the body through skin lesions (even those invisible to the naked eye), respiratory tracts, or mucous membranes.
While there is considerable uncertainty over what would happen if MKPV spilled over - and became endemic - in a new host species, it is a complication we would be better off not having to face.
If we are lucky it might end up being nothing more than a dead-end host, conversely, it might provide a fresh evolutionary pathway for the virus to evolve into something even more formidable.
There are poxviruses in the wild - even in North America - that occasionally spillover into humans (see Alaska Reports 3rd & 4th Case of A Novel Zoonotic Orthopoxvirus (Alaskapox) Near Fairbanks).
And over the past decade we've seen several other novel poxviruses - for which we have limited knowledge - emerge, including:
- Four years ago, in EID Journal: Novel Poxvirus in Proliferative Lesions of Wild Rodents in East-Central Texas, USA we looked at research into a new poxvirus discovered in east-central Texas.
- In 2017, Italian researchers isolated a new pox virus in a cat (see EID Journal Novel Orthopoxvirus and Lethal Disease in Cat, Italy).
- In 2013 two people were found infected with a novel poxvirus in Eastern Europe (and a 3rd from 2010 identified retrospectively) (see NEJM Human Infection with a Zoonotic Orthopoxvirus in the Country of Georgia).
Since the eradication of smallpox in the 1970s, there is a general feeling that poxviruses are a thing of the past, a relic of the 20th century. But viruses have been around far longer than humans, and nature is nothing if not persistent, making it unwise to bet against their long-term success.
While we may not be able to stop these evolutionary processes, the least we can do is to try not to aid and abet them.
