Between 2005 and the end of 2010, the CDC documented 19 human infections by swine origin influenza viruses (SOIV) across the United States, 12 of which were trH1N1 viruses, 6 were trH3N2, and 1 was trH1N2.
During the summer of 2011 a new strain of swine influenza - originally dubbed trH3N2 but renamed H3N2v (swine variant influenza) – was discovered to have evolved in pigs.What made this virus different from the earlier trH3N2 novel strains was that it was a reassortant swine H3N2 which had acquired the matrix (M) gene from the 2009 H1N1 pandemic virus.
Over the next couple of months a handful of human infections were reported in Pennsylvania, Indiana, and Iowa - primarily among children - all with exposures to pigs at state or local fairs.
The CDC’s MMWR on November 23rd of that year detailed the Iowa cases in a dispatch called Limited Human-to-Human Transmission of Novel Influenza A (H3N2) Virus — Iowa, November 2011.
By then it was pretty apparent that this swine H3N2 virus had a greater affinity to human hosts than most of the other SOIVs we’d seen in the past (excluding the 2009 H1N1pdm virus).A few more scattered cases in Minnesota and West Virginia by year's end, and the virus was given a new name WHO/FAO/OIE: Call It A(H3N2)v, which raised the total for 2011 to a dozen cases reported around the country.
This was, in all likelihood, a substantial undercount with at least one estimate putting the number 200 times greater (see CID Journal: Estimates Of Human Infection From H3N2v (Jul 2011-Apr 2012).The following summer (2012) the floodgates opened - and while still likely badly under counted - over a little more than two months more than 300 human swine variant infections were reported across 10 states. Again, nearly all had direct contact with pigs at state and local fairs (see CID Journal: H3N2v Outbreaks In United States – 2012).
While the number of reported swine variant infections dropped back to single digits for each of the next three years (2013, 2014, 2015) in 2016 we saw a renewed surge of cases.An MMWR: Investigation Into H3N2v Outbreak In Ohio & Michigan - Summer 2016 revealed that 16 of the 18 cases analyzed belonged to a new genotype not previously detected in humans.
This year, we've seen another jump in swine variant cases, with 65 novel swine variant infections reported as of November 3rd (see CDC FluView Wk 43: Three More Swine Variant Virus Infections (CO, NE, MI), second only to 2012's record setting outbreak.
While most of these infections have been mild or moderate, a couple of deaths have been reported since 2012, along with a number of hospitalizations. The CDC takes these zoonotic infections seriously, and their Influenza Risk Assessment Tool (IRAT) lists H3N2v as having moderate pandemic potential.
The CDC has published a number of guidance documents for animal exhibitors, venues, and visitors to agricultural exhibits and has sponsored a Public Health Youth Agriculture Education Program, but it isn't easy convincing people that activities that up until recently were considered low risk, suddenly now carry a significantly higher degree of danger.All of which brings us to a fascinating report on KAP (Knowledge, Attitude & Practices) in animal exhibitor's households during last summer's H3N2 outbreak in Michigan and Ohio. I've only included a few excerpts from the open-access report, so follow the link to read it in its entirety.
Do animal exhibitors support and follow recommendations to prevent transmission of variant influenza at agricultural fairs? A survey of animal exhibitor households after a variant influenza virus outbreak in Michigan
R. J. Stewart, J. Rossow, J. T. Conover, E. E. Lobelo, S. Eckel, K. Signs, M. G. Stobierski, S. C. Trock, A. M. Fry, S. J. Olsen and M. Biggerstaff
First published: 16 November 2017Full publication history
DOI: 10.1111/zph.12425 View/save citation
Cited by (CrossRef): 0 articles Check for updates
This work was supported by the Centers for Disease Control and Prevention.
SummaryThe reluctance among animal exhibitors to adopt more stringent infection control procedures is not unlike the push back we've seen among poultry farmers in Asia, and camel owners in Saudi Arabia, who can't quite get their heads wrapped around the idea that their beloved animals could potentially carry a disease that could infect them.
Influenza A viruses circulate in swine and can spread rapidly among swine when housed in close proximity, such as at agricultural fairs. Youth who have close and prolonged contact with influenza-infected swine at agricultural fairs may be at increased risk of acquiring influenza virus infection from swine. Animal and human health officials have issued written measures to minimize influenza transmission at agricultural exhibitions; however, there is little information on the knowledge, attitudes, and practice (KAP) of these measures among animal exhibitors.
After an August 2016 outbreak of influenza A(H3N2) variant (“H3N2v”) virus infections (i.e., humans infected with swine influenza viruses) in Michigan, we surveyed households of animal exhibitors at eight fairs (including one with known H3N2v infections) to assess their KAP related to variant virus infections and their support for prevention measures. Among 170 households interviewed, most (90%, 151/167) perceived their risk of acquiring influenza from swine to be low or very low.
Animal exhibitor households reported high levels of behaviours that put them at increased risk of variant influenza virus infections, including eating or drinking in swine barns (43%, 66/154) and hugging, kissing or snuggling with swine at agricultural fairs (31%, 48/157).
Among several recommendations, including limiting the duration of swine exhibits and restricting eating and drinking in the animal barns, the only recommendation supported by a majority of households was the presence of prominent hand-washing stations with a person to monitor hand-washing behaviour (76%, 129/170).
This is a unique study of KAP among animal exhibitors and highlights that animal exhibitor households engage in behaviours that could increase their risk of variant virus infections and have low support for currently recommended measures to minimize infection transmission. Further efforts are needed to understand the lack of support for recommended measures and to encourage healthy behaviours at fairs.
- Influenza viruses can spread rapidly among swine at agricultural fairs, and youth who participate in these events may be at increased risk of acquiring influenza viruses due to their close and prolonged contact with infected swine.
- Despite recommendations to minimize the transmission of influenza viruses from swine to humans, our survey found that animal exhibitors engaged in behaviours that put them at increased risk of acquiring variant influenza virus, including eating and drinking in swine barns, and hugging, kissing or snuggling with swine during agricultural fairs.
- In our survey, there was little support among households of animal exhibitors for most measures recommended to minimize transmission of influenza from swine to humans. Additional efforts to educate youth animal exhibitors about the risk of infection and benefit of prevention practices may be necessary to increase support for and adherence to recommendations.
And, as a serial cat owner (who owns who is a matter for debate), I understand that.I'm just as guilty of treating my beloved feline companion like a furry family member, even though there is an (admittedly low) potential for cross species disease transmission (see PHE: Transmission Of Bovine TB From Felines To Humans - UK and Avian H7N2 Virus in Human Exposed to Sick Cats).
But disease threats change over time. And no disease evolves faster, or has greater pandemic potential, than influenza.Meaning we must either acknowledge these emerging disease threats and learn to avoid them, or suffer the consequences.