Household Transmission of Human Metapneumovirus and Human Parainfluenza Viruses 1-4 in the United States, 2022-2024

A study examined household transmission of human metapneumovirus (HMPV) and human parainfluenza viruses (HPIV 1-4) in households in Washington and Oregon from June 2022 to March 2024. Among 1,040 households, HMPV occurred in 236 households (23%) and HPIV in 341 households (36%). Secondary attack rates were similar for both viruses: HMPV 8.7% and HPIV 7.3%, with a median time between cases of 7 days. Genetic analysis showed that household cases were very similar to circulating strains during the same period. New cases in households were primarily caused by transmission from children to adults. The findings emphasize the importance of virus spread in schools and childcare settings and support the need for prevention measures targeting children to reduce household transmission.