Streptococcus pneumoniae resulting in hospitalization among residents of long-term care in Toronto, Canada

Background: Streptococcus pneumoniae is an important cause of pneumonia and invasive pneumococcal disease (IPD). Reductions in IPD during the covid-19 pandemic have emphasized the degree to which PD may be a result of person-to-person transmission. We investigated the extent to which PD in long-term care (LTC) homes might be a result of transmission of pneumococci over extended periods of time. Methods: Population-based surveillance of pneumococcal disease (PD) in LTC residents requiring hospitalization was used to identify situations in which 3 or more cases of the same serotype (ST) occurred in one home during a 23 year period. A cluster was defined as being present if the rate of disease due to that ST in that home exceeded the rate due to that ST in all other homes during the same time period. Whole-genome sequencing (WGS) was used to investigate whether cases from epidemiologic clusters were genetically related compared to temporally and geographically matched isolates from community-dwelling adults.