2023: outbreaks of swine influenza

The following outbreaks, which occurred last year, illustrate the reality of zoonotic influenza, the fact that all ages can be vulnerable, that those with and without comorbidities can be at risk, and that various exposures can lead to swine influenza infection. It is interesting to note the way scientists are able to analyse the viruses and fit them within a phylogenic tree showing their relationships and evolution. The diversity of zoonotic influenza viruses that caused human infections in 2023 is alarming and infections of some types of zoonotic influenza viruses caused severe disease with a high mortality rate. In 2023 they did not transmit easily from person to person, although we never know when this may change, and therefore must be ever-ready for a pandemic.

WHO will continue to strengthen surveillance, jointly with its partners, in both animal and human populations, thoroughly investigate every zoonotic infection, build up pandemic preparedness planning, and get better readiness for the next influenza pandemic. Here is a summary of some swine influenza outbreaks notified to WHO last year:


On 7 June 2023, WHO was notified 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. 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 a swine farm. The two contacts did not develop respiratory disease and tested negative for influenza. Sporadic human cases of influenza A(H1N1)v have been reported previously, including from Brazil.

/Public Release. View in full here.