Thanks to Mike Coston for tweeting about this WHO DON: Influenza A(H1N1) variant virus - Brazil. Excerpt:
On 7 June 2023, Brazil notified the World Health Organization (WHO) of a fatal laboratory-confirmed human case of infection with a swine-origin influenza A(H1N1) variant (v) virus in the inner state of Paraná.
Sporadic human cases of influenza A(H1N1)v have been reported previously, including from Brazil. According to the International Health Regulations (IHR) 2005, a human infection caused by a novel influenza A virus subtype is an event that has the potential for high public health impact and must be notified to the WHO.
Based on the information currently available, WHO considers this a sporadic case, and there is no evidence of person-to-person transmission of this event. The likelihood of community-level spread among humans and/or international disease spread through humans is low.
Description of the case
On 7 June 2023, the Brazil IHR National Focal Point (NFP) notified WHO of a fatal human infection caused by a swine-origin influenza A(H1N1)v virus detected by the National Influenza Centre (NIC), Oswaldo Cruz Foundation, Rio de Janeiro.
The patient was a 42-year-old woman with underlying medical conditions who lived near a swine farm. She developed fever, headache, sore throat, and abdominal pain on 1 May 2023 and was hospitalized on 3 May with a severe acute respiratory infection. On 4 May, the patient was admitted to the Intensive Care Unit (ICU) and she passed away on 5 May.
Ongoing investigations reported that the patient did not have any direct contact with pigs, however, two of her close contacts worked at the swine farm. The two contacts did not develop respiratory disease and tested negative for influenza. To date, no human-to-human transmission associated with this case has been identified.
During hospitalization, a nasopharyngeal swab sample was collected from the patient for influenza and SARS-CoV-2 testing, as part of regular respiratory virus surveillance activities. Real-time Polymerase Chain Reaction (RT-PCR) was conducted at the State of Paraná Central Public Health Laboratory, where the sample was subtyped as an influenza A/H1 virus. The sample also tested positive for a swine influenza A virus marker by RT-PCR.
The specimen was forwarded to the National Influenza Centre Oswaldo Cruz Foundation, in Rio de Janeiro, where further complementary analyses and genomic sequencing were performed. Samples received at the NIC on 25 May were confirmed to be an influenza A(H1N1)v virus by sequence analysis on 30 May. The recovered genome has a high identity (99%) with the haemagglutinin (HA) of other Influenza A(H1N1)v viruses previously detected in the municipality of Toledo state of Paraná in 2022. In addition, it has 96% identity with the HA of viruses collected from pigs in Brazil in 2015.
On 8 June, after the Brazilian Ministry of Health (MoH) notified WHO under the IHR, the NIC started the process to send the patient's samples to the WHO Collaborating Centre at the United States Centers for Disease Control and Prevention (US CDC) for further characterization.
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