The role of viral interaction in household transmission of symptomatic influenza and respiratory syncytial virus

Abstract

The role of viral interaction-where one virus enhances or inhibits infection with another virus-in respiratory virus transmission is not well characterized. This study used data from 4029 total participants from 957 households who participated in a prospective household cohort study in Southeast Michigan, U.S.A to examine how viral coinfection and cocirculation may impact transmission of symptomatic influenza and respiratory syncytial virus infections. We utilized multivariable mixed effects regression to estimate transmission risk when index cases were coinfected with multiple viruses and when viruses cocirculated within households. This analysis included 201 coinfections involving influenza A virus, 67 involving influenza B virus, and 181 involving respiratory syncytial virus. We show that exposure to symptomatic coinfected index cases was associated with reduced risk of influenza A virus and respiratory syncytial virus transmission compared to exposure to singly infected cases, while infection with another virus was associated with increased risk of acquisition of these viruses. Exposure to coinfected cases among contacts infected with other viruses was associated with increased risk of influenza B virus acquisition. These results suggest that viral interaction may impact symptomatic transmission of these viruses.

Fig. 1. Bar plots displaying frequencies of serial intervals for secondary cases involved in household illness events, by virus of interest.

a Influenza A virus illness clusters. b Influenza B virus illness clusters. c Respiratory syncytial virus illness clusters.

Fig. 2. Viruses detected during household illness events, by primary virus of interest.

a Other viruses detected during household illness events that involved influenza A virus. b Other viruses detected during household illness events that involved influenza B virus. c Other viruses detected during household illness events that involved respiratory syncytial virus. Source data can be found in Supplementary Tables 15–17, AdV adenovirus, BV bocavirus, HCoV human coronaviruses, HMPV human metapneumovirus, PV parechovirus, PIV parainfluenza virus, RV/EV rhinovirus/enterovirus. *Non-cases are those who were involved in a household illness cluster event for a virus of interest and did not test positive for the virus of interest.

Fig. 3. Four-category exposure variable used in multivariable mixed-effects logistic regression models.

a Exposure category 1 includes household contacts who were not infected with another virus and were exposed to a singly infected index case. b Category 2 includes those who were not infected with another virus and were exposed to a coinfected index case. c Category 3 includes those who were infected with another virus and were exposed to a singly infected index case. d Category 4 includes those who were infected with another virus and were exposed to a coinfected index case. Created in BioRender. Ibiebele, J. (2025) https://BioRender.com/x27o890.