Seasonal epidemics of respiratory syncytial virus (RSV) have a significant global health burden on children worldwide, and the virus is active year-round, with transmission most common in the winter months. Mitigation measures implemented during the COVID-19 pandemic had the unintended consequence of suppressing the RSV epidemic during the winter. This led to a significant decrease in the number of RSV cases observed during the winter of 2020-2021 and an increase in the number of children without any natural immunity to the virus. As the mitigation measures used to control COVID-19 have been relaxed in the latter half of the epidemic, there is a continuing risk that cases of respiratory syncytial virus will increase sharply and unexpectedly.
RSV is a common respiratory pathogen that causes infections of the lungs and respiratory tract. In healthy adults and older children, symptoms include a runny nose, coughing, sneezing, and fever – similar to the common cold. However, the disease has a significant global burden as the second leading cause of death among children under the age of one. Similar to COVID-19, respiratory syncytial virus spreads through droplets from the nose and throat of infected people or contact with tools (i.e. infected objects and surfaces). The COVID-19 pandemic and the non-pharmaceutical interventions implemented to ensure its control have had wide-ranging implications for the epidemiology of many other infectious diseases, including RSV. According to GlobalData forecasts, in the UK, it has been estimated that in 2022 there will be more than 1,900,000 prevalent cases of RSV in children under the age of one year. However, these cases are likely to be an underestimate if the number of RSV cases increases sharply and out of season.
A study by Bardsley and colleagues was published in the journal Lancet Infectious Diseases In September 2022, the impact of non-pharmaceutical interventions targeting COVID-19 on the epidemiology of RSV in England was modeled. Bardsley and colleagues found that at the start of the pandemic, RSV cases declined sharply during the winter of 2020-21, followed by a significant increase in transmission over the following summer. The study found that this was followed by a significant spike in RSV activity in 2021, including a 10.7% increase in hospital admissions and an additional 11,225 laboratory-confirmed cases, equivalent to an increase of 1,258%. Moving away from COVID-19 restrictions has enabled the virus to return to seasonal and typical transmission patterns, particularly among immunologically naive populations.
Bardsley and colleagues found that during the winter of 2020-21 in England, there were 10,280 fewer laboratory-confirmed cases – a 99.5% decrease compared to previous winters before the pandemic. Furthermore, RSV-related hospitalizations decreased by 73.7% among children under five years of age. COVID-19 control measures such as closures, school closures and social distancing, which all limit close contact between young children, largely explain the decrease in RSV transmission during this period.
Because many children had not been exposed during the previous winter, there were more than normal people without natural immunity to RSV who were susceptible to infection, allowing for the unprecedented rates of RSV observed in the summer of 2021. As the epidemic continues, from The important thing is to be aware of the changing epidemiological patterns of RSV and the additional stress this may place on health care services this winter.