Human case of swine-origin influenza A virus detected in Denmark, in keeping with CDC examine

In a current examine revealed within the Rising Infectious Illness Journal, researchers detected a swine influenza A virus (IAV)-infected affected person in routine surveillance on the Nationwide Influenza Middle in Denmark. The detected influenza variant appeared distinct from any variant discovered beforehand in Denmark.

Research: Extreme Human Case of Zoonotic An infection with Swine-Origin Influenza A Virus, Denmark, 2021. Picture Credit score: Liya Graphics/Shutterstock


As per official data, throughout the 2021–22 influenza season, 16,160 instances in Denmark had been because of the influenza A virus, predominantly the H3N2 subtype. Throughout this time, no instances of swine-origin influenza virus occurred in people. For the reason that 2009 influenza A(H1N1) pandemic, no stories of persistent human-to-human IAVs transmission have come to gentle. Additionally, there have been solely sporadic stories of human infections with swine IAVs. But, the zoonotic potential of IAVs is very regarding.

Case report

A younger man in his 50s, working at a swine abattoir in Denmark, was hospitalized after acute onset of sickness on November 24, 2021. He had dizziness within the evening, adopted by chest ache, ache radiating towards the left arm, diarrhea, and malaise, however no fever. The affected person suffered repeated convulsions and needed to be admitted to the intensive care unit (ICU) and placed on air flow to stop seizures and handle declining oxygen ranges.

He had no cardiovascular, kidney, neurological, or different impairment, together with pneumonia, that might rationalize his sudden bout of extreme sickness. Nonetheless, a pharynx swab pattern of the affected person examined optimistic for IAV. Notably, no different coworker on the affected person’s office reported the incidence of influenza.

With antiviral treatment (oseltamivir) and supportive remedies, the affected person’s medical situation improved over the following two days, so he was discharged from the hospital. The researchers submitted the remaining pattern materials to the Danish Nationwide Influenza Middle, which confirmed it was optimistic for the pandemic H1N1 pressure.

Additional evaluation by whole-genome sequencing revealed its consensus sequence to be of the H1N1 subtype. Notably, the virus was extra much like swine IAVs than human influenza strains. The staff uploaded this sequence to the worldwide initiative on sharing all influenza knowledge (GISAID) database.

The sequence had no match to IAV sequences in GISAID, as revealed by the Fundamental Native Alignment Search Software (BLAST) searches; nevertheless, a comparability to in-house sequences of swine influenza viruses from Denmark confirmed a detailed resemblance to 2021 swine IAVs. This viral pressure had a number of genetic and antigenic variations from different influenza A viruses detected in Denmark. Additionally, it had poor reactogenicity to the presently used human seasonal influenza vaccines. Moreover, its phylogenetic analyses revealed that almost all gene segments had been much like the H1N1 subtype. Quite the opposite, its neuraminidase and non-structural segments belonged to the clade 1C avian-like swine influenza A(H1N1) present in Eurasia.


Earlier in Denmark, an aged affected person with comorbidities skilled classical influenza-like sickness (ILI). Nonetheless, the reported case on this examine was distinctive as a result of a beforehand wholesome grownup skilled extreme and sudden sickness. One other distinct remark was that this affected person skilled convulsions, that are uncommon in adults and usually accompanied by fever or encephalitis. Due to this fact, the infecting viral strains in these two instances are seemingly genetically distinct.

Detection of a variant IAV through routine surveillance highlighted the significance of steady monitoring of each human and swine IAVs with zoonotic potential. Moreover, it underscored the necessity to promptly take countermeasures for many who are available contact with swine owing to their occupation and expertise ILI.

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