The article says: "Nobody knows precisely why we are much more likely to catch the flu in the winter months than at other times of the year. Perhaps it’s because flu viruses flourish in cool temperatures and are killed by exposure to sunlight. Or maybe it’s because in winter, people spend more time indoors, where a sneeze or a cough can more easily spread a virus to others."

This is utter egregious bullshit. Less sunlight means less vitamin D. It's as simple as that. If you take 4000 units or more of Vitamin D 3, every day, you won't get the flu.