Cohort Profile: a Prospective Household cohort study of Influenza, Respiratory Syncytial virus, and other respiratory pathogens community burden and Transmission dynamics in South Africa (PHIRST), 2016-2018

Purpose The PHIRST study (Prospective Household cohort study of Influenza, Respiratory Syncytial virus, and other respiratory pathogens community burden and Transmission dynamics in South Africa) aimed to estimate the community burden of influenza and respiratory syncytial virus (RSV) including the incidence of infection, symptomatic fraction, and disease severity, and to assess household transmission. We further aimed to estimate the impact of HIV infection and age on disease burden and transmission, and to assess the burden of Bordetella pertussis and Streptococcus pneumoniae. Participants We enrolled 1684 individuals in 327 randomly selected households in two sites (rural Agincourt subdistrict, Mpumalanga Province and urban Jouberton Township, North West Province) over 3 consecutive influenza and RSV seasons. A new cohort of households was enrolled each year. Eligible households included those with >2 household members where ≥80% of household members provided consent (and assent for children aged 7-17 years). Enrolled household members were sampled with nasopharyngeal swabs twice weekly during the RSV and influenza seasons of the year of enrolment. Serology samples were collected at enrolment and before and after the influenza season annually. Findings to date There were 122,113 potential individual follow-up visits over the 3 years, and participants were interviewed for 105,783 (87%) of these. Out of 105,683 nasopharyngeal swabs from follow-up visits, 1,258 (1%), 1,026 (1%), 273 (<1%), 38,829 (37%) tested positive on PCR for influenza viruses, respiratory syncytial virus, pertussis and pneumococcus respectively. Future plans Future planned analyses include analysis of influenza serology results and RSV burden and transmission. Households enrolled in the PHIRST study during 2016-2018 were eligible for inclusion in a study of SARS-CoV-2 transmission initiated in July 2020. This study uses similar testing frequency and household selection methods to assess the community burden of SARS-CoV-2 infection and the role of asymptomatic infection in virus transmission. Registration Clinical trials.gov NCT02519803