Australian Rotavirus Surveillance Program Annual Report, 2023.

This report from the Australian Rotavirus Surveillance Program describes the circulating rotavirus genotypes identified in children and adults during the period 1 January to 31 December 2023. During this period, 1,942 faecal samples were referred for rotavirus G- and P- genotype analysis; of these samples, 1,781 were confirmed as rotavirus positive. This is the highest number of rotavirus-positive confirmed samples by the Australian Rotavirus Surveillance Program in the past > 20 years of operation of the program. Of these confirmed rotavirus positive samples, 1,554 of 1,781 (87.3%) were identified as wildtype rotavirus, and 226 of 1,781 (12.7%) were identified as the Rotarix vaccine-like strain. G3P[8] was the dominant genotype nationally (n = 1,117/1,554; 71.9%), comprised of both human G3P[8] (n = 662/1,554; 42.6%) and the equine-like G3P[8] variant (455/1,554; 29.3%). Other frequently identified genotypes included G2P[4] (n = 146/1,554; 9.4%), G12P[8] (n = 100/1,554; 6.4%), G1P[8] (n = 40/1,554; 2.6%), G9P[4] (n = 32/1,554; 2.1%) and G8P[8] (n = 21/1,554; 1.4%). Genotype distribution was consistent amongst most jurisdictions, with human G3P[8] and equine-like G3P[8] the two dominant genotypes in all jurisdictions, with the exception of the Northern Territory and Western Australia where G2P[4] (7/103; 6.8%) and G12P[8] (54/241; 22.4%) were the second most dominant genotypes respectively. Consistent with observations in 2022, a small number of unusual genotypes were identified (n = 42/1,554; 2.7%), including G2P[8] (n = 18/1,554; 1.2%), and G3P[4] (n = 6/1,554; 0.4%). The high number of rotavirus positive samples received by the program reflected the notifications for rotavirus disease reported to the National Notifiable Disease Surveillance Service. The ability to monitor the genotypes of rotavirus strains causing disease across ages and across jurisdictions provides important data on assessing the performance of the national rotavirus vaccine program and to inform public health interventions during outbreaks. This Australian Rotavirus Surveillance Program also provides important data to monitor annual variations in genotypic patterns and to provide diagnostic laboratories with quality assurance by reporting incidences of wildtype, vaccine-like, or false positive rotavirus results.