Do Weather, Climate and Environmental Conditions Influence the Spread of the Novel Coronavirus?

Climatological, meteorological and environmental conditions are not the main causes of the first wave of the COVID-19 pandemic. However, questions remain as to whether factors such as temperature, humidity, air quality and ultraviolet light can influence the spread of the SARS-CoV-2 virus and the disease it causes (COVID-19).

Many viral respiratory infections, such as the flu, are characterised by seasonal prevalence peaks and other environmental or meteorological sensitivities. SARS-CoV-2 transmission and COVID-19 severity are likely to follow these same patterns. Environmental conditions could therefore influence where and when the disease re-emerges as well as its severity.

The World Meteorological Organisation (WMO) recently joined forces with a number of international scientific institutions to organise an international virtual symposium on the relationship between meteorological, climatological and environmental factors and the spread of COVID-19. The symposium was attended by more than 400 researchers from 50 countries, representing a wide range of disciplines. Attendees discussed what is known, understood and can be reliably predicted about the influence of environmental variables on the trajectory of the COVID-19 epidemic.

The World Meteorological Organisation (WMO) recently joined forces with a number of international scientific institutions to organise an international virtual symposium on the relationship between meteorological, climatological and environmental factors and the spread of COVID-19

The symposium’s scientific committee—of which I was a member— drew up an outcome statement summarising the key messages conveyed at the event and outlining the future of research on this aspect of the COVID-19 pandemic. The main points of this statement are as follows:

1. Current peer-reviewed scientific publications on the SARS-CoV-2 virus and COVID-19 do not show a robust and consistent association with temperature, humidity, wind, solar radiation, or other meteorological or environmental factors. Some evidence suggests that regulated indoor environmental conditions (e.g. air conditioning), in concert with behavioural factors, indirectly modulates localised spread of the virus. More research is needed on which climatic variables are most critical for understanding the likelihood of their influence and for reducing the risk of disease.
2. Evidence indicates that the population’s exposure to air pollution influences the severity of COVID-19 symptoms. The role of air quality in transmission rates is still under investigation.
3. The seasonality of COVID-19 has yet to be established, given that seasonal signals are difficult to distinguish in this early phase of the pandemic. Experience from other respiratory viruses suggests that a seasonal signal might emerge later as the disease becomes endemic.
4. COVID-19 exemplifies the importance of recognising human-environment interactions and disease prevention. SARS-CoV-2 resulted from a zoonotic spillover event, whereby the pathogen was transferred from wildlife to humans. Human-wildlife interactions increase zoonotic disease risk, as a result of human incursion into wildlands and the displacement of wildlife into urban settings due to habitat destruction.
5. Lessons learned from other climate-sensitive diseases should be taken into account. Strong transdisciplinary collaboration is needed, including disease risk monitoring and data collection for assessing the influence of environmental factors.
6. It is fundamental to understand political and technical decision-makers’ information needs. Researchers must select the most appropriate applications of climate data, models and forecasts to inform decision-making.
7. Current experimental forecasts of COVID-19 must be interpreted with extreme caution, since it has not yet been possible to confirm the predictive power of climatological and meteorological variables for SARS-CoV-2 transmission in a robust manner.

Future Prospects

Global research efforts should continue to explore the interactions of COVID-19 and climatological, meteorological and environmental factors.

Global research efforts should continue to explore the interactions of COVID-19 and climatological, meteorological and environmental factors

To improve research outcomes, efforts are needed to encourage the integration of different disciplines and promote a culture of open data sharing and scientific collaboration.

The role of climatological and meteorological factors will become clearer in the later phases of the pandemic, or when COVID-19 becomes endemic. This will allow for the development of more reliable prediction systems. If, in the future, seasonality and other influences are robustly and consistently determined, then risk monitoring and prediction informed by climatological factors could become particularly important in informing public health responses. This includes identifying the timing and location for vaccination strategies, notably for partially effective or short-effect vaccines, and in the context of multiple-hazard scenarios involving other diseases.