Seven weeks ago (Apr 30th) Manitoba Public Health reported on two unrelated swine variant flu infections - one H1N1v and the other H1N2v - and today they report a 3rd case, this time completing the hat trick with another unrelated case; H3N2v.
Human swine variant infections (H1N1v, H1N2v, and H3N2v) are reported - albeit rarely - around the world. Most, but not all cases, report some contact with swine.
While reports out of Canada have been relatively rare, the United States has reported more than 470 cases over the past dozen years (see chart below), including 4 since the first of the year (see here, here, here, and here).
These spillover infections are thought to be more common than we know, but most mild flu cases go untested, and and are unlikely to be picked up by surveillance. Human-to-human transmission has been reported, but only rarely.
The CDC's IRAT (Influenza Risk Assessment Tool) lists 3 North American swine viruses as having at least some pandemic potential (2 added in 2019).
H1N2 variant [A/California/62/2018] Jul 2019 5.8 5.7 ModerateH3N2 variant [A/Ohio/13/2017] Jul 2019 6.6 5.8 Moderate
H3N2 variant [A/Indiana/08/2011] Dec 2012 6.0 4.5 Moderate
And the CDC's Risk Assessment for these viruses reads:
Sporadic infections and even localized outbreaks among people with variant influenza viruses may occur. All influenza viruses have the capacity to change and it’s possible that variant viruses may change such that they infect people easily and spread easily from person-to-person.
The Centers for Disease Control and Prevention (CDC) continues to monitor closely for variant influenza virus infections and will report cases of H3N2v and other variant influenza viruses weekly in FluView and on the case count tables on this website
Today's statement from Manitoba Public Health follows:
Media Bulletin - Manitoba
June 21, 2021
PROVINCE ADVISES CASE OF H3N2 VARIANT INFLUENZA VIRUS IDENTIFIED IN MANITOBA
Manitoba Public Health advises a single case of H3N2 variant influenza (flu) (H3N2v) has been found in southern Manitoba. The case has been reported to the Public Health Agency of Canada in accordance with international health regulations.
The virus is related to influenza viruses that circulate in pigs. Influenza viruses from pigs do not normally infect humans. However, sporadic human infections with influenza viruses that normally circulate in pigs have occurred. When this happens, these viruses are called ‘variant influenza viruses.’
The case was detected in early June after an individual sought testing after developing an influenza-like illness. The individual experienced mild symptoms, was tested and then recovered. The tests came back negative for COVID-19, but was later identified as a case of human influenza A(H3N2)v through routine influenza surveillance processes.
The case appears to be isolated and is the result of a different influenza virus than previously announced variant influenza cases in late April. The investigations are ongoing to determine how transmission may have occurred. Based on available evidence, the current assessment is that there is no increased risk to people, with no evidence of sustained human-to-human transmission at this time.
While these investigations are ongoing, the current assessment is that there is no increased risk to Manitobans, Canadians or the food supply chain at this time. The viruses are not a food-related illness. They are not transmissible to people through pork meat or other products that come from pigs and there is no risk associated with eating pork.
Health officials, in conjunction with Manitoba Agriculture and Resource Development, have launched a public health investigation to determine the source of the virus and to verify that no spread has occurred. The Manitoba government will also continue working closely with the Public Health Agency of Canada and other partners across Canada to share information about this case.
Anyone who works with pigs or poultry, has influenza-like symptoms, and is seeking testing or treatment is reminded to identify themselves as an agricultural worker to medical officials including at COVID-19 testing sites. This will help to identify any potential additional influenza cases.
In most cases, variant flu viruses have not shown the ability to spread easily and sustainably from person to person. Sporadic human cases of variant influenza have been reported over the past decade in North America. One case of human influenza A(H1N2)v and one case of human influenza A(H1N1)v were reported in Manitoba in late April 2021. These viruses are rarely seen in humans.
The increased respiratory surveillance currently done for COVID-19 and influenza allows Manitoba to continue to monitor for any new cases. Health officials advise the detection of these cases could be occurring for a number of reasons including that increased respiratory surveillance for COVID-19 and influenza that has been occurring during the pandemic. It is also possible that there is a true increase in the number of these cases, possibly occurring from exposure to infected pigs or through subsequent, limited human-to-human transmission.
While rare, influenza can spread from pigs to people and from people to pigs. It is important for people who have contact with pigs to take measures to reduce the spread of influenza viruses between pigs and people.
• Do not take food, drink or other items into pig areas and do not put anything in your mouth in pig areas.• Avoid close contact with pigs that look or act ill or are known or suspected to be sick. This includes minimizing contact with pigs and wearing personal protective equipment like protective clothing, gloves and masks that cover your mouth and nose when contact is required. Call a veterinarian if you suspect illness in pigs.• Wash your hands often with soap and running water before and after exposure to pigs. If soap and water are not available, use an alcohol-based hand rub.• Avoid contact with pigs if you have flu symptoms.• Anyone who is at high risk of complications from influenza should avoid pigs and pig barns. If you develop flu symptoms, call a health-care provider and tell them about your exposure to pigs. The same influenza antiviral drugs used to treat seasonal flu can be used to treat variant influenza virus infections.
For more information on human influenza variant viruses, visit:
Earlier this month, we looked a swine variant H1N2v report from Taiwan, and both Germany and Brazil have reported cases in recent months.
Although North American swine variant viruses are currently believed to pose less of a pandemic threat than the EA H1N1 `G4' swine virus in China (see ECDC Risk Assessment: Eurasian avian-like A(H1N1) swine influenza viruses), anytime a novel virus jumps species and infects a human it is worthy of our attention.