The seasonality of pandemic and non-pandemic influenzas: the roles of solar radiation and vitamin D.
Int J Infect Dis. 2010 Dec;14(12):e1099-105. doi: 10.1016/j.ijid.2010.09.002. Epub 2010 Oct 29.
Juzeniene A asta.juzeniene at rr-research.no, Ma LW, Kwitniewski M, Polev GA, Lagunova Z, Dahlback A, Moan J.
Seasonal variations in ultraviolet B (UVB) radiation cause seasonal variations in vitamin D status. This may influence immune responses and play a role in the seasonality of influenza.
Pandemic and non-pandemic influenzas in Sweden, Norway, the USA, Singapore, and Japan were studied. Weekly/monthly influenza incidence and death rates were evaluated in view of monthly UVB fluences.
Non-pandemic influenzas mostly occur in the winter season in temperate regions. UVB calculations show that at high latitudes very little, if any, vitamin D is produced in the skin during the winter. Even at 26°N (Okinawa) there is about four times more UVB during the summer than during the winter. In tropical regions there are two minor peaks in vitamin D photosynthesis, and practically no seasonality of influenza. Pandemics may start with a wave in an arbitrary season, while secondary waves often occur the following winter. Thus, it appears that a low vitamin D status may play a significant role in most influenzas.
In temperate latitudes even pandemic influenzas often show a clear seasonality. The data support the hypothesis that high fluences of UVB radiation (vitamin D level), as occur in the summer, act in a protective manner with respect to influenza.
Copyright © 2010 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.
Observation by Vitamin D Life
- 2014 Ebola became worse during the Liberia rainy season (summer) = less vitamin D.
- Middle East has the worst influenza during summers – it is so hot that people avoid being outdoors in the middle of the day – even for a few minutes