25.05.2020
Susceptible supply limits the role of climate in the early SARS-CoV-2 pandemic
Modeling InfectiologyTransversal
Baker RE et al
Science
Main result
Based on a comparison with the influenza virus and 2 other coronaviruses, the transmission rate of SARS-CoV-2 seems to be highly dependent on the ambient temperature and specific humidity. The associated R0 could vary from 2.5 to 1.5 depending on these factors. The temperature and specific humidity being linked by the Clausius-Clapeyron relation, the study of one of these two variables is sufficient for the model.
Virus transmission decreases when the specific humidity increases. High rainfall can therefore play a role in the transmission of the virus, particularly in tropical regions.
Furthermore, even if the virus is sensitive to climate, the beneficial effects on the number of infected people and on the height of the peak of the epidemic are not easy to determine. Furthermore, the non-drug control measures put in place (confinement, social distancing, etc.) and the immunity of the population seem to be much more influential parameters with regard to the spread.
Virus transmission decreases when the specific humidity increases. High rainfall can therefore play a role in the transmission of the virus, particularly in tropical regions.
Furthermore, even if the virus is sensitive to climate, the beneficial effects on the number of infected people and on the height of the peak of the epidemic are not easy to determine. Furthermore, the non-drug control measures put in place (confinement, social distancing, etc.) and the immunity of the population seem to be much more influential parameters with regard to the spread.
Takeaways
- Without effective control measures and when the climate becomes cold and humid, we expected to see a higher Covid-19 infection prevalence.
- However, summer weather conditions will not significantly limit pandemic growth.
Strength of evidence Weak
Although the study is based on some other viruses data and on a SIRS propagation model, the sensitivity analysis performed by the authors found robust results. However, the study does not take into account certain parameters such as population density or the types of travel associated with each location, as was the case for humidity levels during the year.
Objectives
Determine the sensitivity of the SARS-CoV-2 virus transmission to the climate and model its impact on the spread of the epidemic.
Method
The authors configured a SIRS (Susceptible-Infected-Recovered-Susceptible) propagation model, based on known data from two other coronaviruses (HcoV-HKU1 and HcoV-OC43) concerning the dependence of the transmission rate on the climate and the duration of post-infection immunity.
3 hypothesis are presented:
→ SARS Cov-2 has the same climate sensitivity as the flu
→ SARS Cov-2 has the same climate sensitivity as Hcov-OC43
→ SARS Cov-2 has the same climate sensitivity as HcoV-HKU1
These scenarios are studied in several regions of the world, presenting different characteristics in terms of temperature and humidity.
3 hypothesis are presented:
→ SARS Cov-2 has the same climate sensitivity as the flu
→ SARS Cov-2 has the same climate sensitivity as Hcov-OC43
→ SARS Cov-2 has the same climate sensitivity as HcoV-HKU1
These scenarios are studied in several regions of the world, presenting different characteristics in terms of temperature and humidity.
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