Reports of human infection with novel swine variant influenza (H1N1v, H1N2v & H3N2v) are fairly rare, although due to their (often) unremarkable presentation, and limited laboratory testing, likely occur more often than we know.
The H3N2v strain is by far the most common, making up 94% of all reported cases (n=354) in the United States over the past 11 years. H1N1v comes in 2nd, with 20 cases (4%).
H1N2v is the least common, with just 6 cases reported (the most recent in Minnesota last May) up until today.
While H1N2v still trails the pack, today's FluView reports 2 more cases; one currently hospitalized patient in Wisconsin, and another case - already recovered - from last April in Minnesota.
First today's report, then I'll have more.
Two human infections with novel influenza A viruses were reported to CDC during week 25.In 2015 we learned of 7 swine variant infections (4 - H1N1v & 3 - H3N2v), while last January we saw 1 report of H3N2v from New Jersey.
One human infection with a novel influenza A virus was reported by the state of Wisconsin. The person was infected with an influenza A (H1N2) variant (H1N2)v virus. The patient was hospitalized as a result of their illness, and continues to recover. Direct contact with swine in the week preceding illness onset was reported. No ongoing community transmission has been detected.
One human infection with a novel influenza A virus was reported by the state of Minnesota. In April 2016, the person was infected with an H1N2v virus. The patient was not hospitalized and has fully recovered from their illness. No human-to-human transmission has been identified and the case reported close contact with swine in the week prior to illness onset.
Early identification and investigation of human infections with novel influenza A viruses are critical so that the risk of infection can be more fully appreciated and appropriate public health measures can be taken. Additional information on influenza in swine, variant influenza infection in humans, and strategies to interact safely with swine can be found at http://www.cdc.gov/flu/swineflu/index.htm.
During the summer and early fall of 2012, more than 300 people – mostly linked to county and state fairs in the Mid-West - were diagnosed with one of three swine variant flu strains (H1N1v, H1N2v, and H3N2v).
While we’ve not seen sustained or efficient spread of these swine variant viruses in humans - like all flu viruses - swine variant viruses are capable of evolving, reassorting, and adapting to their hosts.
Since the influenza subtypes that commonly circulate in swine (H1, H2 & H3) are also the same that have caused all of the human pandemics going back 130 years (see Are Influenza Pandemic Viruses Members Of An Exclusive Club?), they are generally regarded as having less far to `jump’ to humans than many avian viruses.
Which is precisely how the H1N1 pandemic virus emerged in 2009, after kicking around (and reassorting in) swine herds for a decade or longer.
People who raise, or work with pigs are probably at greatest risk of infection, but County and State Fair animal exhibits also provide opportunities for these viruses to jump to humans.
The CDC offers the following advice to the public.
CDC Recommendations For People At High Risk:
If you are not at high risk, take these precautions:
- If you are at high risk of serious flu complications and are going to a fair where pigs will be present, avoid pigs and swine barns at the fair. This includes children younger than 5 years, people 65 years and older, pregnant women, and people with certain long-term health conditions (like asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions).
- Don’t take food or drink into pig areas; don’t eat, drink or put anything in your mouth in pig areas.
- Don’t take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.
- 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 close contact with pigs that look or act ill.
- Take protective measures if you must come in contact with pigs that are known or suspected to be sick. This includes wearing personal protective equipment like protective clothing, gloves and masks that cover your mouth and nose when contact is required.
- To further reduce the risk of infection, minimize contact with pigs in the pig barn and arenas.
And for more on swine and swine variant influenza, you may wish to revisit some of these blogs: