Covid-19: Weather Factors
Executive Summary
The spread of covid-19 shows little sign of subsiding even as a vaccine appears on the horizon. Age, blood type, ethnicity, food, sanitation, and social habits all play a role in the spread of infectious diseases (WHO, 2020). This piece investigates the relationship between daily covid-19 deaths and the weather factors temperature & humidity.
A Poisson regression reveals a negative relationship between daily covid-19 deaths and temperature & absolute humidity. Humidity also appears to have a stronger association with daily covid-19 deaths than does the temperature. The findings may prove valuable in understanding the trend in covid-19 deaths, as well as assisting decision-makers in anticipating demand for healthcare services as temperature and absolute humidity decrease moving into winter.
Hypothesis Formulation
A significant proportion of covid-19 cases have occurred in the northern hemisphere (Caramelo et al., 2020). The northern hemisphere with lower temperatures has also witnessed a growth in the rate of infection approaching winter. In contrast, the southern hemisphere has not seen the same phenomenon. A question worth pursuing then is how meteorological characteristics such as temperature & humidity modulate the duplication time of covid-19.
Results
Figure 1 is a comparison of the number of daily covid-19 deaths among selected European countries.
Overall, these countries experienced an upward trend in April. France recorded the highest number of daily covid-19 deaths on the 10th of April with 1,101 fatalities. The distributions are positively skewed, which means the number of daily covid-19 deaths started to decrease following the peak–although the rate is increasing again.
Figure 2 displays a comparison of the same data for temperature.
The average daily temperature is negatively skewed, which means temperature gradually increases in the selected European countries from mid-April.
Considered together, temperature increases from March to August, while the number of daily covid-19 deaths decreases during the same period. This leads to the hypothesis that an increase in the temperature is correlated with a decrease in the number of covid-19 deaths. This relationship is statistically examined in the next section. A similar observation and thus line of reasoning is made with absolute humidity. Figure 3 is provided for completeness.
The number of daily covid-19 deaths is a discrete variable with a unimodal and skewed distribution. This type of data lends itself to a Poisson analysis, where the relationship between temperature & absolute humidity is correlated with the number of daily covid-19 deaths.
Table 4 shows the results of the Poisson regression. According to the table, both independent variables, temperature & absolute humidity have a p-value of less than 0.0001. The null hypothesis can, therefore, be rejected. In other words, there is evidence to suggest the presence of a relationship between the number of daily covid-19 deaths and the weather factors temperature & absolute humidity. The results indicate that for every one-unit increase in temperature, the predicted log count of the number of daily covid-19 deaths increases by 0.030. At the same time, for every one-unit increase in absolute humidity, the expected log count of the number of daily covid-19 deaths decreases by 0.174 units.
Conclusion
The analysis began with an exploration into the relationship between daily covid-19 deaths and the weather factors temperature & absolute humidity. A Poisson regression analysis followed, with the findings suggesting a weak positive relationship between the number of daily covid-19 deaths & temperature, as well as a stronger negative relationship between the number of daily covid-19 deaths and absolute humidity.
Other studies have suggested that when temperature increases, the protein of covid-19 breaks down due to heat intolerance, which is the result of the virus cover in a lipid bilayer. Like temperature, humidity is also a weather variable, which could affect the spread of the virus. This is demonstrated by the fact that once a pathogen is expelled from the respiratory tract (i.e. when sneezing), it can stay in the air for a longer period in the presence of low humidity (Schoeman & Fielding, 2019).
Winter is expected to bring a decrease in temperature and absolute humidity. An accurate understanding of how this may affect the spread of covid-19 is crucial to providing policymakers and healthcare providers the tools necessary to make better-informed decisions.
References
World Health Organization. (2020). Novel coronavirus (2019-nCoV) situation reports. https://www.who.int/emer agencies/diseases/novel-coronavirus-2019/situation-rep orts Wu, J. T
Caramelo, F., Ferreira, N., & Oliveiros, B. (2020). Estimation of risk factors for COVID-19 mortality Preliminary results. Preprint at Med R XIV. https://doi.org/10.1101/ 2020.02.24.20027268
Schoeman, D., & Fielding, B. C. (2019). Coronavirus envelope protein: Current knowledge. Virology Journal, 16(1). https://doi.org/10.1186/s12985-019-1182-0