Elisa Pérez

Influenza A can cause influenza in humans, birds, pigs, and other mammals. In 2009 and 2010, a pandemic caused by the pdm09 strain—popularly called 'swine flu' because it contained genetic sequences from avian, swine, and human influenza—caused thousands of human deaths worldwide. Since then, this lineage has crossed over 370 times from humans to pigs in the United States, according to a study published in PLOS Pathogens. The research also indicates that the circulation of the virus among pigs may cause further evolutionary changes in this lineage, which would increase the risk of the virus passing back to humans.

Analysis of the two asymptomatic cases of H5N1 avian influenza detected in Spain in autumn 2022 in workers at a poultry farm in Guadalajara has confirmed the theory that no actual infections occurred, but that both were in contact with genetic material of the virus found in the environment. Spain has recently modified its protocols, according to the analysis published in Eurosurveillance.