Department of Radiation Biology, Institute for Cancer Research, the Norwegian Radium Hospital, Oslo University Hospital, Montebello, N-0310 Oslo, Norway.
Int J Infect Dis. 2010 Dec;14(12):e1099-105. doi: 10.1016/j.ijid.2010.09.002. Epub 2010 Oct 29.
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.
紫外线 B（UVB）辐射的季节性变化导致维生素 D 状态的季节性变化。这可能影响免疫反应，并在流感的季节性中发挥作用。
研究了瑞典、挪威、美国、新加坡和日本的大流行和非大流行流感。根据每月 UVB 辐射量评估每周/每月流感发病率和死亡率。
在温带地区，非大流行流感主要发生在冬季。UVB 计算表明，在高纬度地区，冬季皮肤几乎无法产生维生素 D。即使在 26°N（冲绳），夏季的 UVB 也比冬季多四倍左右。在热带地区，维生素 D 光合作用有两个较小的峰值，几乎没有流感的季节性。大流行可能在任意季节开始出现一波，而第二次浪潮通常在下一个冬季出现。因此，似乎维生素 D 状态低下可能在大多数流感中起重要作用。
在温带地区，即使是大流行流感也常常表现出明显的季节性。这些数据支持了一个假设，即高强度的 UVB 辐射（维生素 D 水平），如夏季的辐射，对流感具有保护作用。
