Understanding Potential Drivers of Seasonal Transmission of Respiratory Viruses by Examining COVID-19 Pandemic-Driven Disruptions

Respiratory viruses, including influenza, respiratory syncytial virus (RSV), human metapneumovirus (HMPV) and rhinovirus, contribute significantly to global health and economic burdens. While these viruses typically cause mild symptoms, they can lead to severe illness and even death, particularly among vulnerable groups such as young children, the elderly and those who have underlying medical conditions. These viruses are often referred to as "seasonal" due to their predictable patterns of circulation, typically peaking during winter months in countries like the UK. However, the COVID-19 pandemic disrupted these regular transmission cycles. During the pandemic's acute phase, many respiratory viruses became absent due to strict public health measures, and their subsequent reappearance was marked by atypical transmission patterns, including changes in timing, age distribution, and disease severity.

In this PhD I aim to explore the potential drivers of seasonal transmission of respiratory viruses, leveraging the unique disruptions caused by the COVID-19 pandemic. To do this, I will explore different aspects that could influence the timing and oscillation of seasonal respiratory virus circulation. Mathematical models will be designed and developed to investigate biological or sociological reasons for changes in post-pandemic seasonal respiratory virus circulation. These include exploring temporary vertical immunity by investigating the potential impact of disrupted maternal immunity on RSV disease rates in young children, social mixing with children by identifying the role of school closures in the resurgence of seasonal respiratory virus transmission, and virus-virus interactions by examining the potential down-stream implications of introducing an RSV immunisation programme on transmission of other seasonal respiratory viruses.

The research method will significantly contribute to the development of quantitative skills. In addition, the approach to the research question will be multidisciplinary since elements of public health, virology, and immunology as well as statistics and computer programming will be considered. Therefore, depth of knowledge will be obtained on infectious disease modelling and breadth of knowledge will also be acquired due to the nature of the research and the working environment.

Developing a deeper understanding of the drivers of seasonality is important as it helps explain how the wintertime landscape of respiratory viruses is established. Such insights will not only enhance healthcare planning-critical given the acute strain these viruses place on public health systems-but also inform the design of more effective public health interventions, such as immunisation strategies.