Why is flu spreading in winter?

There are several reasons for this: more promiscuous and less aeration promotes the spread, the more energy used to heat weakens the body and lack of sunshine reduces the natural production of vitamin D by the body so that it can not strengthen the immune system.

Some diseases are spreading in winter and not in summer. The researchers at N.I.H. have a hypothesis verified by experiments.

Mixovirus Influenza virus is coated with cholesterol, a very thin oily consistency which varies with temperature. When it's cold, it hardens and provides temporary protection against ambient air and the cold. The virus can survive in open air for some time and move from one organism to another.
Instead, during hot weather, the fat film became soft and so naked, the virus can not survive.

In the body, particularly in the lungs, the virus is in his element, the body heat melted the fat and it can proliferate.

Other causes are:

• Crowding and poor ventilation.
• The cold which mobilizes the resources of the organization.
• The lack of vitamin D.
  It is produced naturally by the body from sunlight, which are rare in autumn and winter, besides the fact that people comes out less often.

Conclusion

In winter, you must alter your diet to increase intake of vitamin D.