Knowledge regarding the dynamics of the COVID-19 pandemic is of great importance and urgency to governments around the world. Key decisions, with significant economic consequence, are strongly influenced by epidemiological forecasting models, and the spread-modifying factors associated with the physical environment must be accounted for in these forecasts. In the context of known inter-personal transmission mechanisms, among susceptible individuals, in the current wave of the pandemic, how environmental factors should be incorporated into epidemiological models and scenarios remains contested. Early analyses of environmental associations with case increase rates, total case counts, and mortality rates from COVID-19 have yielded mixed and inconclusive results. This can be attributed to a combination of a short data record, limitations in the quality and interpretability of case data, varying methodological approaches, the rapid expansion of the novel disease across the globe, in susceptible populations, the complexity of identifying and disentangling environmental drivers from other factors, and the fact that no country has yet experienced a full year of climate seasonal variation while exposed to SARS-COV-2.
The disease originally manifested in the Northern Hemisphere in early to mid-winter, in places with temperate climates, and spread east and west in an initially quite narrow climate band. This could reflect a climate sensitivity, but could just as plausibly reflect trade and human movement patterns. Indeed, some countries currently facing the highest COVID-19 burdens are located in the tropics and subtropics.
Numerous studies have been released (many not yet peer-reviewed), on this and related topics and hence there is a substantial amount of un-tested information available and a great deal of uncertainty around this issue. Some organizations have commenced with the production of operational data and information, including environmentally-informed forecasts. In this context, there is strong risk of misinterpretation and misleading application in public policy. The fastest way both to filter through this information, and to deal with the uncertainty in this regard, will be to bring the appropriate experts together in a meeting to consider and interrogate the evidence and agree on a common way forward.