LAUSR

Respiratory Syncytial Virus (RSV) is a leading cause of lower respiratory tract infection worldwide. The report of temporal changes in the risk of transmission among close contacts has been scarce. This study aims to examine an association between the viral load trajectory and transmission risk to develop a better control strategy for the disease spread. We conducted a household-based prospective cohort study in Biliran Province, the Philippines, and enrolled 451 participants for observing the development of acute respiratory infection. Including the cases found at the health care facility, we analyzed the data of viral loads with symptom records obtained from 172 followed-up participants whose household member was RSV positive with a rapid test during an RSV outbreak in 2018-2019. We developed a model estimating a temporal change of the viral shedding from the infection and evaluated transmission dynamics. We revealed that most transmission events occurred within approximately 7 days from the household exposure, including potential pre-symptomatic transmissions. The inferred risk of infection among those younger than 5 years old was 3.5 times higher than that of those older than 5 years. This finding suggested that the initial week after the household exposure is particularly important for preventing RSV spread.