Household transmission dynamics of human respiratory syncytial virus in China: A multicentre epidemiological and molecular study.

ObjectivesTo estimate the secondary HRSV infection proportion, age-specific susceptibility, inferred spread, and HRSV-A/B transmission patterns in Chinese households.MethodsThis prospective case-ascertained household cohort in Zhejiang, China (November 2024-December 2025) recruited medically attended, laboratory-confirmed paediatric HRSV index cases aged 0-14 years. Ten-day exposure histories, Day 3/10 contact sampling, and regression models assessed household- and contact-level risk factors.ResultsAmong 179 households with 542 contacts, secondary infection was detected in 110 households (61.5%) and 218 contacts (40.2%); 46.3% were symptomatic. Children aged 0-5 years accounted for 86.6% (155/179) of inferred primary cases. Contact infection was highest among children aged 0-5 years (86.4% [38/44]), including all infants aged