In 2014, two unusual peaks of H1N1 influenza outbreak occurred in Nakhon Ratchasima Province, in Thailand. Among 2,406 cases, one of the 22 deaths in the province included a 6-year-old boy, who initially presented with acute necrotizing encephalopathy. On the other hand, his sibling was mildly affected by the same influenza virus strain, confirmed by whole-genome sequencing, with one silent mutation. Absence of acute necrotizing encephalopathy and other neurological illnesses in the family and the whole province, with near identical whole viral genomic sequences from the two siblings, and an absence of concomitant severe lung infection (cytokine storm) at onset suggest nonpermissive infection as an alternative pathogenetic mechanism of influenza virus.
Keywords: acute necrotizing encephalopathy; influenza.