Follow the Sun: Slower COVID-19 Morbidity and Mortality Growth at Higher Irradiances

17 Pages Posted: 3 Apr 2020 Last revised: 5 Dec 2022

See all articles by Alex Bäcker

Alex Bäcker

Ab Inventio, The Invention Factory; Drisit; QLess

Date Written: April 2, 2020


The effect of temperature and irradiance on COVID-19 will determine the course of the pandemic in warmer locations and whether rising temperatures will change its course, and has implications for public health policy. We show case and death counts had significantly lower growth rates at higher temperatures (>14 °C) when aligned for stage in the epidemic. We show irradiance and in particular solar zenith angle in combination with cloudopacity explain COVID-19 morbidity and mortality growth better than temperature. COVID-19 exploded during the darkest January in Wuhan in over a decade. Daily irradiance correlated with case growth 7 days later. Our results suggest transmission models should incorporate irradiance, that the impact of natural and artificial UV irradiance on individual morbidity and mortality should be tested, and has implications for the best locations and optimal behaviors for high-risk individuals and COVID-19 patients to weather the pandemic: following the Sun.

Note: Funding: Self-funded.

Conflict of Interest: No competing interests to declare.

Keywords: COVID-19, coronavirus, temperature, irradiance, sunlight

Suggested Citation

Bäcker, Alex, Follow the Sun: Slower COVID-19 Morbidity and Mortality Growth at Higher Irradiances (April 2, 2020). Available at SSRN: or

Alex Bäcker (Contact Author)

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