Michigan Reports Two Influenza Swine Variant Infections (H3 & H1N2) - WHO & CDC Updates

[Michael Coston]

Michigan: Oakland County Fair Reports Influenza A Infection In Pigs



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While avian flu viruses (e.g. H5N1, H5N6, H3N8, etc.) are currently viewed as our biggest zoonotic flu threat, not all that far behind are the swine variant viruses (typically H1, H2, H3 viruses), which occasionally spill over from pigs to humans, mostly during the summer and fall `agricultural fair season'.

Swine are viewed as excellent `mixing vessels' for influenza viruses, due to having both mammalian α2,6 receptor cells and avian-like α2,3 receptor cells, and having frequent contact with humans and birds. They are often infected with human seasonal flu, along with their own swine flu viruses.

It is this ability that has recently raised concerns that avian H5N1 might find pigs to be a suitable host (see Netherlands Risk Assessment & Warning of Swine As `Mixing Vessels' For Avian Flu), a concern bolstered last May by the discovery of the (H5N1) Seroconversion of a Swine Herd at a `mixed species' farm (poultry & swine) in Italy.

Although most (H1, H2, and H3) swine variant infections have been mild or moderate, a few deaths have been reported since 2012, along with a number of hospitalizations. 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 Moderate
H3N2 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

In 2021 the CDC ranked a Chinese Swine-variant EA H1N1 `G4' as having the highest pandemic potential of any flu virus on their list (see EID Journal: Zoonotic Threat of G4 Genotype Eurasian Avian-Like Swine Influenza A(H1N1) Viruses, China, 2020).

In recent months we've looked at swine variant reports from Taiwan and Brazil, but surveillance around the globe is spotty at best, and the United states has reported just shy of 500 cases (n=495) since 2010.

Today's report from Oakland County officials isn't about a human infection, but rather the discovery that pigs displayed at a county fair agricultural exhibit (which ran from July 7-16, 2023) have tested positive for influenza A (subtype not given).

It is a little surprising that 3 days after the discovery the subtype has not been identified, although a full genomic analysis can take much longer. Hopefully those details will be available soon.

Meanwhile county health officials are engaged in contact tracing of exhibitors, and are also warning the public to be aware of potential exposure, and to seek medical advice if they become symptomatic.

The full press release follows:

Influenza Detected in Pigs at Oakland County Fair

Post Date:07/17/2023 4:57 PM

Pontiac, Mich., – The Michigan Department of Agriculture and Rural Development and Department of Health and Human Services have notified Oakland County Health Division that several pigs present at the Oakland County Fair tested positive for influenza A virus, the causative agent of swine influenza.

The pigs began displaying symptoms on July 14 at the fair which took place July 7-16 at Springfield Oaks County Park in Davisburg and is organized and managed by the Oakland County 4-H Fair Association. The swine barn closed to the public that evening. No human cases of swine flu have been reported in Michigan this year. The Health Division is working with state partners and fair management to contact trace and monitor exhibitors and fair staff who were exposed. In the meantime, out of an abundance of caution, the county is notifying the public who may have visited the swine barn.

“Fairgoers who visited the swine barn and develop respiratory symptoms are encouraged to talk to a health care provider and report potential exposure to infected swine,” said Dr. Russell Faust, Oakland County medical director. “Physicians are reminded to consider swine influenza in persons presenting with symptoms, even during the warmer months when seasonal influenza cases are low.”

Swine influenza (flu) is a respiratory disease in pigs caused by type A influenza viruses. Swine flu viruses don't usually infect humans, but human infections have been reported. People cannot get swine influenza from eating properly prepared pork or handling pork products – only from contact with an ill pig.

Symptoms of swine flu in people are like seasonal flu and may include fever, cough, runny nose, and sometimes body aches, nausea, vomiting, or diarrhea. Symptoms usually appear within three days of exposure but can occur for up to 10 days. On rare occasions, swine flu in humans can lead to severe illness such as pneumonia or death.

Those at higher risk of developing complications if they get swine influenza include children younger than 5 years, people 65 years and older, pregnant women, and people with certain chronic health issues, such as asthma, diabetes, heart disease, weakened immune systems and neurological conditions. There is no vaccine for swine flu, and the seasonal flu vaccine will not protect against it. Antiviral drugs such as Tamiflu and Relenza, however, are effective in treating swine flu. Early treatment works best and may be especially important for people with a high-risk condition.

Additional subtyping, including whole genome sequencing, will be performed by the National Veterinary Services Laboratories (NVSL) in Ames, Iowa. The expected turnaround time is approximately three weeks.

For media inquiries only please contact Bill Mullan, Oakland County public information officer, at 248-858-1048.

The CDC advises those who are at higher risk of serious flu complications (including children under 5, adults over 65, pregnant women, and those with certain chronic medical conditions), to avoid pigs and the swine barn altogether.

Due to growing concerns, last month the CDC held a webinar for clinicians on recognizing, treating, and reporting zoonotic (avian & swine) influenza cases in the community (see COCA Call : What Providers Need to Know about Zoonotic Influenza).

While the public health risk from swine flu viruses is currently thought to be low, these viruses continue to reinvent themselves as they circulate in pigs, which makes them unpredictable and worthy of our attention.

https://afludiary.blogspot.com/2023/07/michigan-oakland-county-fair-reports.html

[Michael Coston]

Michigan: MDHHS Reports Presumptive-Positive Swine Variant Infection From Oakland County Fair





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Nine days ago (see Michigan: Oakland County Fair Reports Influenza A Infection In Pigs) we looked at a report on the detection of Influenza A in pigs at a country fair which ran from July 7-16. The subtype was not provided, and samples had been sent on to the National Veterinary Services Laboratories (NVSL) in Ames, Iowa.

While Swine-variant (typically H1N1v, H1N2v, H3N2v) infections are generally mild, and don't transmit very well between people, they are assumed to have at least some pandemic potential, and so local officials urged:

“Fairgoers who visited the swine barn and develop respiratory symptoms are encouraged to talk to a health care provider and report potential exposure to infected swine,” said Dr. Russell Faust, Oakland County medical director. “Physicians are reminded to consider swine influenza in persons presenting with symptoms, even during the warmer months when seasonal influenza cases are low.”

Today we are learning from the MDHHS that at least one person - a swine exhibitor at the fair from neighboring Lapeer County, Mi. - has been identified as a probable swine-variant infection. We also learn that the virus has been partially identified as `H3'.

First the statement from the MDHHS, then I'll return with a bit more.

MDHHS reports presumptive positive case of influenza A H3 (swine flu) variant detected in Lapeer County resident

July 26, 2023
The Michigan Department of Health and Human Services and Lapeer and Oakland County health departments have identified a presumptive positive human case of influenza A H3 variant (swine flu) in a Lapeer County resident who was an exhibitor at the Oakland County Fair. The fair took place July 7-16 at the Springfield Oaks County Park in Davisburg. A respiratory specimen that tested presumptive positive for swine flu will be sent to the Centers for Disease Control and Prevention (CDC) for confirmatory testing.

Oakland County Health Division has been reaching out to swine exhibitors and their families who visited the swine barns at the Oakland County Fair to identify any additional illnesses in those who may have been exposed to influenza from infected pigs. Oakland County Health Division has already alerted providers in their jurisdiction to watch for patients presenting with respiratory symptoms who report exposure to swine or who visited the fair.

“Visitors of the Oakland County Fair should monitor for flu-like symptoms: fever, respiratory symptoms like cough and runny nose, and body aches, nausea, vomiting or diarrhea,” said Dr. Natasha Bagdasarian, MDHHS chief medical executive. “If you believe you may have the flu, contact your health care provider and stay home until you have recovered.”

Below are some steps you can take to protect yourself and prevent the spread of any illness:Avoid close contact with sick people.

• Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
• Wash hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
• Refrain from eating or drinking in livestock barns or show rings.
• Do not take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.
• Anyone who is at high risk of serious flu complications and planning to attend a fair should avoid pigs and swine barns.
• Avoid touching your eyes, nose, and mouth. Germs spread this way.
• If you are sick, stay home from work or school until your illness is over.
• Avoid contact with pigs if you have flu-like symptoms. Wait seven days after your illness started or until you have been without fever for 24 hours without the use of fever-reducing medications, whichever is longer.
• Get an annual influenza vaccination.

Pigs may be infected with swine influenza viruses that are different from human flu viruses. Swine flu viruses spread among pigs and – while rare – they can spread from pigs to people too. Spread of swine flu viruses from a pig to a person is thought to happen in the same way that human flu viruses spread; mainly through droplets when infected pigs cough and sneeze.

Symptoms of variant influenza infection in people are similar to those of seasonal flu viruses and can include fever and respiratory symptoms, such as cough and runny nose, and possibly other symptoms, such as body aches, nausea, vomiting or diarrhea. Infections with influenza viruses (including variant viruses like influenza A H3) can sometimes cause severe disease, even in healthy people.

Severe illness can include complications, such as pneumonia, which may require hospitalization, and sometimes causes death. People who are at high risk of developing complications if they get variant influenza infection include children younger than 5 years of age, people 65 years of age and older, pregnant women and people with certain long-term health conditions, such as asthma, diabetes, heart disease, weakened immune systems and neurological or neurodevelopmental conditions.

The time period it takes from exposure to illness for variant influenza is similar to that of seasonal influenza, which can be up to 10 days, but is most commonly three days. Currently, there is no human vaccine for influenza A H3 and the seasonal flu vaccine will not protect against Influenza A H3; however, prescription antiviral drugs, such as oseltamivir and zanamivir, are effective in treating influenza A H3 virus infections. Early treatment works best and may be especially important for people with a high-risk condition.

For more information, visit CDC.gov/SwineFlu

While lengthy, surprisingly few details on this case provided by this press release.

• The age, gender, presentation (mild or severe), and current condition of the infected individual are not addressed.
• Nothing is said about the patients close contacts, or why it has taken > 10 days for the first case to be identified
• It is also a bit unusual that nearly 2 weeks after the discovery of the sick pigs, the full subtype remains unidentified; as it is still being reported only as `H3'.

While most `H3' swine viruses are `H3N2', new genotypes occasionally emerge (see MMWR: Investigation Into H3N2v Outbreak In Ohio & Michigan - Summer 2016), and sometimes, we even see novel subtypes.

In 2014 we saw `H3N1' identified in at least two states (see USDA IAV-S Surveillance Program Detects Novel H3N1 In US Swine). H3N1 had been known to circulate in pigs for at least a decade (see EID Journal 2006 article Novel Swine Influenza Virus Subtype H3N1, United States), but that new variant was a combination of both human and swine influenza viruses.

So we'll be particularly interested in the results of genomic analysis of this sample from Ames, Iowa.

Due to growing concerns over swine and avian flu, last month the CDC held a webinar for clinicians on recognizing, treating, and reporting zoonotic influenza cases in the community (see COCA Call : What Providers Need to Know about Zoonotic Influenza).

While the public health risk from swine flu viruses is thought to be low, these viruses continue to reinvent themselves as they circulate in pigs, which makes them unpredictable and worthy of our attention.

https://afludiary.blogspot.com/2023/07/michigan-mdhhs-reports-presumptive.html

[Michael Coston]

WHO Update & Risk Assessment On H1N2v Case - United States



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Over the past 3 weeks we've seen two human infections with swine-variant (H3v & H1N2v) viruses reported from Michigan, both associated with agricultural exhibits at county fairs, from two different counties (Oakland & Tuscola).

Although we see sporadic cases every summer (and many more likely go undetected), spillovers of swine viruses are followed closely by health authorities because of their (currently low) potential to spark an epidemic or pandemic.

The CDC's Investigation found:

Presumptive positive influenza A(H3)v virus infection

The Michigan Department of Health and Human Services first reported a presumptive positive influenza A(H3) variant virus infection on July 26 in a person who attended a fair that took place July 7-16. A respiratory specimen from that patient was sent to CDC and received on July 27. Diagnostic testing conducted at CDC was inconclusive, likely due to the respiratory specimen not containing enough virus. However, it is likely the patient was infected with an influenza A(H3)v virus given the presumptive positive test results from Michigan, as well as the epidemiologic findings of the local investigation.

An investigation into this first infection found that:

• • The patient was exposed to pigs within 10 days prior to illness onset at an agricultural fair where swine influenza A virus was detected among pigs.
  • The patient was treated with flu antivirals.
  • The patient was not hospitalized and has recovered from their illness.
  • Additional investigation did not identify respiratory illness in any of the patient’s close contacts or household contacts.
  • To date, no person-to-person spread of this virus has been identified.

Confirmed influenza A(H1N2)v virus infection

The Michigan Department of Health and Human Services notified CDC of a specimen that tested positive for influenza A but lacked reactivity with diagnostic tests for contemporary human influenza viruses representing either H1pdm09 or H3 subtypes on July 31. A respiratory specimen from that patient was sent to CDC and received on August 2. This was confirmed at CDC to be an influenza A(H1N2)v virus infection. This occurred in a person who attended a different fair, which took place July 23-29.

An investigation into the second infection found that:

• • The patient was exposed to pigs within 10 days prior to illness onset at another agricultural fair.
  • The patient was treated with flu antivirals.
  • The patient was not hospitalized and is recovering from their illness.
  • Additional investigation did not identify respiratory illness in any of the patient’s close contacts or household contacts.
  • To date, no person-to-person spread of this virus has been identified.

Over the past dozen years we've seen nearly 500 swine variant cases (H1N1v, H1N2v, H3N2v) reported by the CDC, and two months ago the CDC held a webinar for clinicians on recognizing, treating, and reporting zoonotic influenza cases in the community (see COCA Call : What Providers Need to Know about Zoonotic Influenza).

Prior to 2017, H1N2v was the least commonly reported swine-variant virus (of the top 3), but over the past 6 years it has outpaced H1N1v & H3N2v by a wide margin. Internationally, we are seeing an uptick as well (see here, here, and here).

Overnight the World Health Organization published their own update on the Michigan H1N2v case. I've posted some excerpts below, but you'll want to follow the link to read it in its entirety. I'll have a brief postscript after the break.

Influenza A(H1N2) - United States of America
11 August 2023

Situation at a glance:

On 4 August 2023, the United States International Health Regulations (IHR) National Focal Point informed PAHO/WHO of a human infection with a novel influenza A(H1N2) variant virus identified in the State of Michigan. This was confirmed by Reverse Transcription Polymerase Chain Reaction at the United States (US) Centers for Disease Control and Prevention (CDC) on August 2.

The case was not hospitalized and is recovering from the illness. Investigations by local public health officials identified swine exposure by the patient at an agricultural fair.
(SNIP)

The case was not hospitalized. Investigation by local public health officials identified swine exposure by the patient at an agricultural fair, that took place between 23 and 29 July, within 10 days prior to illness onset. Additional investigation did not identify respiratory illness in any of the patient’s close contacts or household contacts. No additional cases were identified related to this agriculture fair. No person-to-person transmission of influenza A(H1N2)v virus associated with this case has been identified. No additional cases of human infection with A(H1N2)v virus have been identified as of 10 August 2023.

This is the first influenza A(H1N2)v virus infection identified in the United States this year. Since 2005, there have been 512 influenza A variant virus infections (all subtypes), including 37 (human infections with influenza A (H1N2)v viruses reported in the United States.

Epidemiology of the disease:

Swine influenza A(H1N2) viruses circulate in swine populations in many regions of the world. Influenza A viruses that normally circulate in swine are called “variant” influenza viruses when isolated from humans.1 Human infections are usually due to direct or indirect exposure to pigs or contaminated environments. There may be important antigenic and genetic differences between seasonal influenza viruses that circulate worldwide in the human population and influenza viruses that normally circulate in swine. Close monitoring is needed to early identify changes in the virus and/or its transmission to humans.2

Non-seasonal or zoonotic influenza viruses infecting humans may cause disease ranging from mild conjunctivitis to severe pneumonia and even death; usually, these human infections of zoonotic influenza are acquired through direct contact with infected animals or contaminated environments. Since 2005, 37 human infections with influenza A(H1N2)v virus, including this one, have been reported in the United States.

Public health response

The public health response efforts led by local officials included enhanced surveillance for cases. The county health department conducted active case finding by reaching out to fair exhibitors and their families to ascertain additional illnesses. In addition, local providers were notified to watch for respiratory illness in persons who had attended the fair or had recent contact with swine.
WHO risk assessment

Swine influenza A viruses circulate in swine populations in many regions of the world. Depending on geographic location, the genetic characteristics of these viruses differ. When an influenza A virus that normally circulates ihttps://www.who.int/emergencies/disease-outbreak-news/item/2023-DON482n swine (but not people) is detected in a person, it is called a “variant influenza virus”. Most human cases are the result of exposure to swine influenza A viruses through contact with infected swine or contaminated environments. Because these viruses continue to be detected in swine populations around the world, further human cases can be expected.

According to the IHR, a human infection caused by a novel influenza A virus subtype is an event that has the potential for high public health impact. A novel influenza A virus is considered to have the potential to cause a pandemic if (1) the virus has demonstrated the capacity to infect and transmit efficiently among humans, and (2) differs from currently circulating seasonal human influenza viruses (i.e., A/H1 or A/H3), circulating widely in the human population such that the hemagglutinin (HA) gene (or protein) is not a mutated form of those; and (3) the population has little to no immunity against it.

To date, only sporadic human infections caused by influenza A(H3N2), A(H1N1) and A(H1N2) variant viruses have been reported in the United States, and there has been no evidence of sustained human-to-human transmission. Human infections with influenza variant viruses tend to result in mild clinical illness, although some cases have been hospitalized with more severe disease. Given the potential impact on public health, human infections with these viruses need to be monitored closely. In this event, there was no reported evidence of sustained human-to-human transmission, the illness was mild and no further influenza variant virus transmission in the community has been identified.

There has been some limited, non-sustained human-to-human transmission of variant influenza A viruses, although ongoing community transmission has not been identified. Current evidence suggests that these viruses have not acquired the ability of sustained transmission among humans. The risk assessment will be reviewed if needed should further epidemiological or virological information become available.

Influenza A viruses that infect pigs are different from human influenza A viruses. Currently, there is no vaccine for Influenza A(H1N2)v infection licensed for use in humans. Thus, influenza vaccines against human influenza viruses are generally not expected to protect people from influenza viruses that normally circulate in pigs.

(Continue . . . )

Although swine influenza surveillance is quite limited around the world, 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 Moderate
H3N2 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

The CDC currently ranks a Chinese Swine-variant EA H1N1 `G4' as having the highest pandemic potential of any flu virus on their list.

The CDC routinely advises those who are at higher risk of serious flu complications (including children under 5, adults over 65, pregnant women, and those with certain chronic medical conditions), to avoid pigs and the swine barn altogether.

https://afludiary.blogspot.com/2023/08/who-update-risk-assessment-on-h1n2v.html