Pavitra Roychoudhury, Anna Elias-Warren, Erica Wetzler, Hyeong Geon Kim, Kevin Kong, Hong Xie, Cassey Spring, Margaret G Mills, Alex Harteloo, Collrane Frivold, Madison Hollcroft, Mark Drummond, Tara Hatchie, Erica Clark, Brenna Ehmen, Peter D Han, Luis Gamboa, Sally Grindstaff, Jeremy Stone, Katherine L Hoffman, Alexander L Greninger, Lea M Starita, Christina Lockwood, Janet A Englund, Ana A Weil, Sacha L Reich, Richard A Mularski, Mark A Schmidt, Jennifer L Kuntz, Allison L Naleway, Helen Y Chu
Human metapneumovirus (HMPV) and human parainfluenza viruses (HPIV 1-4) are common causes of seasonal respiratory illness, but their household transmission dynamics remain poorly defined. We analyzed weekly symptom data and nasal swabs from a prospective household surveillance study in Washington and Oregon from June 2022 to March 2024. Swabs were tested for HMPV and HPIV, and a subset underwent whole-genome sequencing. Distinct index cases occurred in 236 (23%) and 341 (36%) of 1,040 households for HMPV and HPIV, respectively. Household secondary attack rates (SAR) and median generation times were similar for HMPV (8.7%, 7 days) and HPIV (7.3%, 7 days). Sequenced samples reflected contemporaneous circulating strains during the same period, with household sequences clustering closely together. High-quality viral whole genome sequences were recovered for two or more individuals within a household in a total of 26 households for HMPV and 45 households for HPIV. Intra-household pairwise nucleotide (nt) distance ranged from 0 to 14 nt (median 0) for HMPV and 0-8 nt (median 1) for HPIV when cases occurred 0-15 days apart. Transmission occurred primarily from children to adults, emphasizing the importance of childcare- and school-associated spread and supporting child-focused prevention strategies to reduce household transmission.