The distribution of community outbreaks of the current global pandemic shows
seasonal patterns associated with latitude, temperature, and humidity, which is
similar to the behavior of seasonal viral respiratory tract infections.

The seasonality of many viral infections is associated with a lack of sunlight, which results in low 25(OH)D concentrations and an uptick in diseases such as respiratory syncytial virus (RSV) infection.[2]^,[3]^,[4] While it’s obvious that winter in temperate climates interferes with sufficient exposure to ultra violet rays, the rainy season in tropical climates also results in low UVB exposure.

Low levels of vitamin D can cause immune dysfunction, including lack of antibody production and increased risk of inflammation. With regard to respiratory function, low levels of vitamin D are associated with numerous pulmonary diseases, including acute lung injury and acute respiratory distress syndrome. Vitamin D and its receptors have been shown to protect epithelial…