September 2025 | Canadian Food Inspection Agency | by Cathy Furness and Rod Lister
Since December 2021, Canada has been dealing with a nationwide outbreak of highly pathogenic avian influenza (HPAI). Since the initial outbreak, over 14 million farmed and domestic birds have been impacted. The outbreak has also spread to other animals, including seals, cats and other farm animals.
In March 2024, the outbreak took an unexpected turn when HPAI was found in dairy cattle in the United States (U.S.). The predominant HPAI virus (genotype B3.13) found in U.S. dairy cattle has not been detected in birds, cattle or any other animals in Canada (to date as of June 2025). However, this discovery has raised concerns about the spread of HPAI in mammals and other species highlighting the need to protect Canadians and Canada’s livestock from HPAI.
Taking action
In response, the Canadian Food Inspection Agency (CFIA) has taken several actions to protect Canada’s dairy cattle and milk supply. This includes:
- working with dairy farmers to identify signs of HPAI in their herds and know who to contact if they suspect infection
- voluntary testing of cows not showing clinical signs of HPAI and providing guidance to veterinarians
- implementing additional requirements for Canadian cattle returning from a temporary stay in the U.S.
- adding import restrictions on cattle from the U.S.
The CFIA is also monitoring milk produced in Canada to support early detection of HPAI in Canadian dairy cattle. CFIA began testing commercial milk in May 2024, and shifted to raw, unpasteurized milk collected at dairy processors in August. By November 2024, testing was underway in all provinces. As of June 2025, the CFIA has tested 1211 retail milk samples and 5,077 raw milk samples from 2700 dairy farms across Canada. The latest testing results are available on the CFIA website. Currently, only fluid raw milk is subject to surveillance. All samples to date have tested negative, and there is no evidence of HPAI in Canada’s milk supply.
Why we sample milk
Milk is a valuable tool for surveillance because it is collected from multiple dairy farms in Canada on a regular basis. When dairy cows get sick with flu, instead of showing respiratory signs, they shed a lot of virus in the milk. Sampling milk helps detect the presence of HPAI in dairy cattle early on, even in animals that are not showing signs of sickness, which allows for the CFIA to take appropriate action.
How testing works
The surveillance system is designed to sample a representative number of farms distributed across Canada. Here’s how it works:
- A 10mL sample of raw milk is taken from a given number of trucks at select dairy processors.
- Once the predetermined number of monthly samples have been taken, CFIA food inspectors collect the samples and send them to a CFIA lab, like the Ottawa Laboratory (Fallowfield) or the Lethbridge Laboratory.
- A real-time polymerase chain reaction (RT-PCR) test is used to screen milk samples. It is a very sensitive test to detect genetic material in the milk.
- Additional tests would be applied to determine the exact strain of the virus if the first screening test is positive.
- Results of testing are shared with trading partners, as well as the public via social media and on the CFIA website.
A positive sample means that genetic material was found. Finding a virus's genetic material doesn't mean the sample contains active viruses that can harm people or animals. It also doesn't mean the milk sample would contaminate animals or people that come in to contact with milk sample. To date, all samples tested from both retail and raw milk have been negative in RT-PCR tests.
What would happen if a sample came back positive
If HPAI was detected in a milk sample, the CFIA would trace the source by collecting samples from each farm that contributed milk to the truck, all of which would be tested. Once identified, the herd on the identified farm would be considered affected.
Following the identification of the affected herd, the relevant province or territory, together with CFIA and industry, would work together to prevent further spread by requiring that:
- personal safety and on-farm biosecurity measures are followed
- cattle movement (particularly lactating cattle) onto and off the premises is restricted or limited until the herd is cleared from the disease
- no milk from clinically-affected animals enters the bulk tank and is appropriately discarded
- any milk not discarded because it is being fed to other animals undergoes an inactivation process
- all milk from the bulk tank goes for pasteurization
- epidemiological information pertaining to the infected herd is collected
- local public health authorities are involved to further assess any potential human health risk
An affected herd may be considered no longer affected once they meet the following minimum criteria (additional provincial requirements may also apply) including:
- initially, waiting a minimum of 30 days after the initial HPAI detection, and confirming a minimum of 14 days has elapsed since clinical signs have resolved in the herd.
- then, once the above points have been met, verifying that herds with lactating dairy cattle produce two consecutive negative herd tests, conducted 14-21 days apart. Note that a herd test includes samples from all lactating animals in the herd.
Protecting Canada’s cattle population from HPAI is a collective effort. The risk of HPAI transmission to humans remains low, and commercially sold milk and milk products remain safe to consume. The Government of Canada, the provinces and territories, farmers and other industry stakeholders will continue to work together to actively monitor, prepare and respond quickly as the situation evolves to help safeguard Canada’s cattle and protect Canadians.