RSV and rhinovirus increase pneumococcal carriage acquisition and density, whereas nasal inflammation is associated with bacterial shedding

Highlights•Primary RSV or rhinovirus infection predisposed to pneumococcal carriage•Asymptomatic RSV infection increased bacterial colonizing density by 2-log•Nasal inflammation associated with pneumococcal shedding via the nose•Adults may also act as a reservoir of pneumococcal transmissionSummaryEpidemiological studies report the impact of co-infection with pneumococcus and respiratory viruses upon disease rates and outcomes, but their effect on pneumococcal carriage acquisition and bacterial load is scarcely described. Here, we assess this by combining natural viral infection with controlled human pneumococcal infection in 581 healthy adults screened for upper respiratory tract viral infection before intranasal pneumococcal challenge. Across all adults, respiratory syncytial virus (RSV) and rhinovirus asymptomatic infection confer a substantial increase in secondary infection with pneumococcus. RSV also has a major impact on pneumococcal density up to 9 days post challenge. We also study rates and kinetics of bacterial shedding through the nose and oral route in a subset. High levels of pneumococcal colonization density and nasal inflammation are strongly correlated with increased odds of nasal shedding as opposed to cough shedding. Protection against respiratory viral infections and control of pneumococcal density may contribute to preventing pneumococcal disease and reducing bacterial spread.Graphical abstract