There is still much to be understood about the factors influencing the ecology and epidemiology of COVID-19. In particular, whether environmental variation is likely to drive seasonal changes in SARS-CoV-2 transmission dynamics is largely unknown. In a study published in Proceedings of the National Academy of Sciences of the United States of America (PNAS), the effects of the environment on SARS-CoV-2 transmission rates as investigated.
The study showed that temperature and population density can be important factors in transmission but only in the absence of mobility-restricting policy measures, although particularly strong policy measures may be required to mitigate the highest population densities. By combining epidemiological models and outputs with spatial climate data, the findings show that environment (specifically, cold, but also the correlated low-humidity conditions) can enhance the transmission of SARS-CoV-2.
The results comparing SARS-CoV-2 transmission rates before and during lockdown support the idea that the major driver of transmission is public health policy. Summer weather is no substitute for mitigation and policy can prevent transmission in the winter. Remember the lockdown and stay-at-home orders that we all resisted and complained about? Maybe, just maybe they saved lives after all! Stay well, stay informed, and stay tuned!