Taiwan CDC Reports 2nd Case of Swine-Origin H1N2v Infection

 

#17,153

In June of 2021 Taiwan reported their first swine variant (H1N2v) infection (see Taiwan CDC Reports Human Infection With Swine Variant H1N2v Virus) in a 5-year-old girl. That report indicated that that 3 of the patient's contacts had `flu-like' symptoms, but they were unable to identify H1N2v in any of them.

As we've discussed often, swine variant infections in humans - while believed to be rare - undoubtedly happen more frequently than we know. Testing for, and subtyping of, influenza viruses is only rarely done - particularly in those with mild disease.

Today Taiwan's CDC has announced a 2nd case, this time in a 7-year-old girl with mild influenza who lived in the central region. As with the previous case, among her 6 closest contacts, 2 had reported flu-like symptoms, but H1N2v was not detected in any of them.

Note: We don't know the exact timing of the testing of these contacts, which might have adversely affected the ability to detect a specific subtype. Their CDC states, however, `There is no evidence of human-to-human transmission'. 

Analysis of the virus indicated it was similar - but not identical - to previously sequenced swine-origin H1N2v viruses.  The (translated) report from Taiwan's CDC follows, after which I'll return with a bit more. 

The second case of H1N2v influenza virus isolated from a respiratory disease patient in China has been recovered. The CDC urges the public to manage their personal health

Release date: 2022-12-05

The Centers for Disease Control and Prevention stated today (5) that it received a report from the hospital in October 2022 that a type A influenza virus that could not be subtyped was isolated from the respiratory specimen of a 7-year-old girl with mild influenza who lived in central China , which was further tested and sequenced by the department as H1N2v influenza virus.

After investigation, there were 6 close contacts of the case, 2 of whom had flu-like symptoms, and no H1N2v influenza virus infection was found after inspection. After inviting the agricultural administration unit and relevant medical experts to hold a meeting to discuss, based on the above-mentioned existing epidemiological investigation results, the case was judged. It should be a sporadic case, which is similar to past international cases. There is no evidence of human-to-human transmission. The health and agricultural authorities will continue to strengthen the monitoring of humans, animals and the environment.

The Centers for Disease Control and Prevention pointed out that this case is the second case of H1N2v influenza virus in my country. The case has no recent travel history abroad, and his family is engaged in poultry farming. On September 24 this year, he developed symptoms such as fever, muscle aches, loss of appetite, cough and runny nose. , On September 26, he went to the doctor due to a high fever. The rapid COVID-19 test was negative and the rapid influenza test was positive for type A. After the doctor's evaluation, he did not need to be hospitalized. He returned home after prescribing influenza antiviral drugs and has recovered.

The CDC further pointed out that the H1N2v influenza virus was isolated from the girl's respiratory specimen on October 18, and tests for common viruses in respiratory infections such as adenovirus, respiratory fusion virus, enterovirus, and rhinovirus were all negative. . In addition, the agricultural administration unit also collected specimens from pigs in the pig farm run by the case family, and the results showed that no H1N2 influenza virus was detected. In response to the second confirmed case in my country, the CDC will simultaneously notify the World Health Organization through the IHR contact window.

According to the CDC, the first case of H1N2v type A influenza in my country was detected in April last year (2021). It was a 5-year-old girl who lived in the central region. The source of feed and pigs, the slaughterhouse where the livestock is raised, the route of the transport vehicle, and the gene of the virus are all different, and the two cases are determined to be unrelated.

H1N2v is a low-pathogenic influenza virus that exists in pigs, and there are occasional cases of human infection reported, and most of them are mild. Since 2011, there have been at least 45 confirmed cases of H1N2v influenza in the world, with 41 cases in the Americas. Most of the cases have a history of contact with pigs or exposure to contaminated environments. There is no case of infection through eating meat. The gene sequence of the virus isolated from the patient this time is similar to the H1N2 virus strain isolated from pigs in the past, but not the same. It is sensitive to the current public-funded influenza antiviral drugs.

The CDC reminds that to prevent the new type A influenza, the public should abide by the "5 Dos and 6 Don'ts" principle. and contact history, those who have long-term contact with poultry and livestock should be vaccinated against influenza, have a balanced diet and exercise properly; "6 don'ts": do not eat raw poultry eggs or products, do not smuggle or buy meat from unknown sources, do not touch or feed Livestock, do not release or discard livestock at will, do not mix livestock with other livestock, and do not go to places with poor air circulation or crowded places. For relevant information, please visit the global information website of the CDC (https://www.cdc.gov.tw/), or call the free epidemic prevention hotline 1922 (or 0800-001922).

Prior to 2017, the H1N2v strain of swine flu was only rarely reported, with H3N2v far outpacing it.  Since 2017, H1N2v has become far more common, with numerous cases reported in the United States, along with scattered cases reported from Canada, Brazil, and France. 

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 

While 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).

So far, the good news is that currently circulating swine variant viruses haven't become biologically `fit' enough spark a pandemic. In order to be successful, they need to be able to replicate and transmit on par with already circulating human flu viruses. 

The bad news is there are an unknown number swine-variants spreading - and reassorting - among hundreds of millions of pigs around the world, and most of that goes on out of our sight.   

And as with the last swine-flu pandemic (2009), the first sign that a swine-variant virus has made the leap to a pandemic may not come until days or even weeks after it has begun its world tour.