Foodborne acute gastroenteritis outbreak associated with a rare norovirus recombinant GII.10[P16] genotype, Brazil, 2023

BACKGROUND Norovirus is a major cause of acute gastroenteritis (AGE) outbreaks worldwide. On 1 August 2023, the health surveillance agency of Espírito Santo received a notification of a set cases of AGE from patients who attended an event organised by the Municipal Health Department. A local catering company provided lunch on 30 July (30 lunch boxes). The menu provided included macaroni, rice, tropeiro beans and cooked potatoes. The ingredients used in the preparation of tropeiro beans were beans, banana, cabbage, sausage and cassava flour. Diarrhoea, nausea, vomiting, abdominal pain, headache and weakness were the main reported symptoms peaking between 30 and 31 July. OBJECTIVES In the present study, we aimed to establish the agent responsible for a gastroenteritis outbreak during a lunch event in Espírito Santo State, Brazil. METHODS Stool samples (n = 5) of AGE patients were analysed by real-time quantitative polymerase chain reaction (RT-qPCR) to detect rotavirus A (RVA) and norovirus GI/GII. For norovirus molecular characterisation an open reading frame (ORF)1-2 junction region was used. FINDINGS All samples tested positive for norovirus GII, showing high viral loads. Rotavirus and norovirus GI were not detected in any of the samples. Norovirus sequencing identified a rare recombinant genotype GII.10[P16] as the cause of the outbreak. Norovirus sequences from specimens from five individuals shared 100% of nucleotide (nt) identity and had the highest nt similarity with a South Africa GII.10 strain detected in 2020. MAIN CONCLUSION This is the first report of a rare GII.10[P16] recombinant norovirus strain in Brazil.