As the unprecedented outbreak of H5N1 avian influenza continues in North America, there are numerous concerns about where the outbreak is heading and threats to other species, including domestic and wild mammals, and people (the latter being just another “domestic mammal”).  My inbox is filled with questions about different concerns and scenarios. The one I’ll address today is about risks to veterinary clinics that treat backyard poultry.

Backyard poultry are increasingly common in many areas.  Since they are typically kept outdoors and not managed with anywhere near the same degree of biosecurity as most commercial poultry, they are at high risk of exposure to avian flu when it’s circulating in wild birds in the area, as it is right now.

The good news about the current H5N1 influenza outbreak:

This H5N1 strain is not well adapted to infect humans, or mammals in general. It lacks some of the genetic material that makes other flu virus more transmissible to and between people. Only a couple of human infections with this strain have been reported, including one person infected with H5N1 in the US in whom the only symptom was fatigue. Transmission to other non-avian species is probably rare too, but all we can say is “probably” because of limited testing of wildlife. Spillover has occurred, including the recent cases of H5N1 influenza in fox kits in Ontario. Whether these infections are really rare events or just rarely diagnosed isn’t clear and remains a big question. Still, it’s safe to say that, at this point, spillover risks are limited.

(Some of) the concerning parts about the current H5N1 influenza outbreak:

It’s still a flu virus, and flu viruses change. The circulating strain can evolve and reassort (swap genes with other flu viruses) anytime. We have plenty of other flu viruses circulating in North America, including seasonal human flu and flu in other species such as pigs, horses and (in the US) dogs. There are also other avian flu strains around here and there. The more flu viruses in circulation, the greater risk of them getting together to reassort and make a new strain, potentially with more affinity for people.

So, back to veterinary clinics treating backyard poultry:

Like all domestic animals, backyard poultry sometimes need veterinary care, and this often falls to small animal or mixed animal veterinary clinics, since there are only a small number of specialist poultry veterinarians in Ontario (and many do not treat backyard birds, for several reasons including biosecurity risks). Unlike most livestock, backyard poultry that need veterinary care may be taken to the clinic (in contrast to most livestock where the veterinarian visits the farm). This creates a few concerns that need to be taken into consideration by the clinic when it comes to avian influenza.

Risk of transmission to people

  • Fortunately, as noted above, transmission to people is rare, at least at this point. Rare doesn’t mean it can’t happen, but the odds of clinically significant bird-to-human infection seems to be very low. It’s not likely someone handling an infected bird will get sick, but it’s possible.
  • We also need to think about the potential impact of people who have human flu getting exposed to birds that might have avian flu. If one infects the other (and therefore has an infection with two different flu viruses), that’s the recipe for re-assortment to create a new strain. We might be getting into excessively theoretical issues here (I doubt it, though), but hopefully the “stay home if you’re sick” message is getting across.  Unfortunately we know that’s not always the case, and people who are infected with influenza don’t always have symptoms.

A comment I made today to someone was “There’s some degree of risk but in the absence of sick birds, the zoonotic risk isn’t likely any greater than that posed by your average new puppy (e.g. Campylobacter).” I think that’s a fair statement, but at the same time, one of my goals in life is not to become a case report describing a rare/new infectious disease, so I still want to take care.

Risk of transmission to mammals

  • The issues with risk to other mammals are similar to humans (in the end we’re just another mammal, afterall). The risk of transmission is low but not zero. I wouldn’t get too concerned about it, but I’d still rather not create the chance for rare bird-to-mammal transmission in the clinic, especially since we can largely prevent it with some basic infection control measures (see below).

Risk of transmission to other birds

  • This is probably my main concern. There could be transmission to other backyard poultry (not too likely, since there usually aren’t multiple backyard chickens at a clinic at the same time) or transmission to other pet birds. Susceptibility amongst different bird species varies, but we’re seeing lots of wild birds dying from this virus. We don’t want to see it spread in a clinic to someone’s pet bird (or worse, to someone’s aviary). That creates risk of illness and death for the bird(s), and more human exposure to the virus.

So, what do we do?  We do what we do every day: We assess and manage risk.

We can never 100% eliminate risk of infectious disease in a clinic setting, especially flu. However, we can use some basic, common sense measures to reduce risk of avian flu transmission.

Risk assessment

Since healthy looking birds can be infected, there’s no way to guarantee that a given bird isn’t shedding avian flu virus. However, we can identify situations where the risk is higher and increase the infection control measures that are used. Higher risk situations include:

  • The bird is sick with signs that are compatible with avian flu infection (including neurological disease)
  • Other birds in the group are sick
  • Other birds in the group have died
  • Avian flu has been found in wildlife in the area, and the bird has outdoor access

Physical separation

If we can keep poultry away from people and animals as much as possible, we greatly reduce the risk of pathogen transmission. That can be done a few ways:

  • Admitting birds directly to isolation or another separate, contained space (versus hanging around in the waiting room)
  • Examining birds outside so they never set foot in the clinic
  • Housing hospitalized birds in isolation or a separate area

Limiting contact

Minimizing the number of people who handle the birds in the clinic to the one or two who might be required for examination and procedures reduces transmission points.

Appointment scheduling

It’s not always possible to have poultry come into the clinic at a time when no other birds are present if there’s a high bird caseload or for emergencies, but it’s something that should be done whenever possible.

PPE and hand hygiene

Routine infection control practices can go a long way, and are used based on the assumption that any patient might be harbouring something infectious.  Things like wearing proper protective outwear (basic lab coat) and hand hygiene help a lot. Protective measures can be increased if there’s more risk (see above) to include a disposable gown, mask and eye protection.


Accurate rapid tests for avian flu would be very useful and are available in some other jurisdictions. However, we have not had success getting approval to import the tests for screening birds in places like clinics and wildlife rehab facilities. Rapid tests (as we learned from COVID-19) are not perfect and can never rule out flu. However, they could be a useful screening measure, as a positive would indicate a need to use stricter precautions, and to get confirmatory testing done while providing more surveillance info. There was reluctance to use rapid tests for COVID-19 initially, but they ended up being a very useful tool. Currently, the only testing available for avian flu is PCR testing through diagnostic labs, which doesn’t help us from a clinic control standpoint since the turnaround time can be a few days.

The current H5N1 avian flu outbreak is definitely something to be concerned about. It’s having major impacts on domestic and wild birds. We want to control it to reduce the impact on those population and reduce the risk of this developing into something more. However, vet erinary clinics should be able to treat poultry without much risk, if some basic infection control measures are used.

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