Human influenza A with swine origin
On this page
- What is swine influenza
- What are H1N1v, H1N2v, and H3N2v
- Animal-to-human spread
- How we monitor swine influenza
What is swine influenza
Swine influenza (swine flu) is an infectious respiratory disease of pigs. It's caused by type A influenza viruses.
Signs of influenza in pigs can include:
- not eating
- eye redness
- coughing (barking)
- difficulty breathing
Some pigs infected with influenza may not show any signs of illness at all.
Swine flu viruses don't normally infect people, but there have been infrequent exceptions.
What are H1N1v, H1N2v, and H3N2v
H1N1, H1N2 and H3N2 are types of flu viruses that commonly circulate in North American swine herds.
When a virus that circulates in pigs is found in people, it's called a variant. This is indicated by using a lowercase ‘v' at the end of its name. H1N1v, H1N2v and H3N2v are variant viruses of type A influenza.
Human infections of influenza A with swine origin usually occur after direct or indirect exposure to infected pigs.
When an infected pig coughs or sneezes, its respiratory droplets spread through the air. If you're nearby and you inhale the infected droplets, you can become infected.
You can also get infected if you touch something with the virus on it and then touch your own mouth or nose.
Human influenza A with swine origin isn't a food-related illness. You can't get it from eating properly handled and prepared pork or other products that come from pigs.
Cases of human influenza A with swine origin are rare. To date, there's no evidence of sustained person-to-person spread.
Worldwide, occasional cases of H1N1v, H1N2v, H3N2v have been reported in humans since 2005, with some larger localized outbreaks of H3N2v associated with human contact with swine at agricultural fairs reported in the past decade. In Canada, there has only ever been two confirmed cases of H1N1v, only three confirmed cases of H1N2v and only two confirmed cases of H3N2v. These include:
- One case in Ontario (September 2012).
- One case in Manitoba (April 2021)
- One case in Alberta (October 2020)
- One case in Manitoba (April 2021)
- One case in Manitoba (December 2021)
- One case in Ontario (October 2016)
- One case in Manitoba (June 2021)
These (H1N1)v viruses differ from the now seasonal influenza A(H1N1) virus that emerged from swine back in 2009.
Based on current evidence in Canada, the risk to human health is low.
The Public Health Agency of Canada reports any cases of human influenza A with swine origin that are notified globally and within Canada each month in Human Emerging Respiratory Pathogens Bulletin.
Infections of human influenza A with swine origin usually result in mild respiratory illness. Symptoms are similar to those of seasonal flu.
Initial symptoms usually include:
These symptoms are quickly followed by:
- runny nose
- watery eyes
- muscle aches
- loss of appetite
- throat irritation
In some cases, people (especially children) may also experience:
- vomiting or diarrhea
Most people recover within 10 days. In some cases, more severe complications can develop, such as pneumonia. These cases may require hospitalization.
Cases of human influenza A with swine origin are diagnosed through a patient's symptoms, signs and laboratory testing.
A swab is taken from the nose or throat during the first few days of illness. This swab is sent to a provincial laboratory, where it's tested to identify the virus. If a new or variant virus is detected, the sample is sent onwards to the National Microbiological Laboratory for confirmatory testing and further analyses.
The same antiviral drugs used to treat seasonal flu may be used to treat human influenza A with swine origin.
Antiviral drugs may:
- reduce flu symptoms
- shorten the length of illness
- possibly reduce serious complications
Antiviral drugs don't provide immunity against human influenza A with swine origin infections.
To protect yourself and others from human influenza A with swine origin:
- keep shared surfaces and objects clean
- wash your hands frequently and thoroughly
- stay home if you're sick and get plenty of rest
- avoid touching your nose, mouth or eyes with your hands
- cough and sneeze into the bend of your arm, not your hand
- keep your immune system strong by eating healthy foods and being active
You should take special precautions if you:
- own a farm
- live on a farm
- work on a farm
- have contact with pigs
These precautions include:
- avoiding close contact with pigs that look or act ill
- wearing personal protective equipment if you must come in contact with ill pigs, including:
- masks that cover your mouth and nose
- protective clothing
If you have flu-like symptoms:
- avoid contact with livestock, particularly sick animals
- contact a health care provider (ex: your regular physician) for more information
The flu shot is recommended by NACI for everyone 6 months and older. If you're involved in the food production system or agricultural settings, getting a seasonal flu shot each year can help reduce the spread of flu viruses between people and animals. It can also protect everyone involved in the food production system, including:
- farm workers
- feed truck drivers
- farm service personnel
- producers and their families
- vaccination and insemination crews
- visitors to swine farms and swine operations
How we monitor swine influenza
We monitor swine origin influenza A variants like A(H1N1)v, A(H1N2)v, and A(H3N2)v regularly. We work closely with our national and international partners to track and report influenza activity in Canada and around the world.
The Public Health Agency of Canada reports any cases of human influenza A with swine origin that are notified globally and within Canada each month in the Human Emerging Respiratory Pathogens Bulletin.
FluWatch is Canada's national surveillance system that monitors the spread of the flu and other flu-like illnesses on an ongoing basis. Reports that contain information on flu activity in Canada are posted each week.
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