Why are Colds and Flus Seasonal?

We all know that colds and flus are viruses, which are small infectious agents that replicate inside the living cells of living organisms. They generally spread throughout the population through coughing and sneezing and other forms of physical contact or proximity. Viruses can't reproduce on their own, they need to use the inner-workings of our cells to produce multiple copies of themselves. Essentially, they are a parasite.

So, if a virus acts like a parasite, and only needs a host body to carry on its lifecycle, why is it that there is a Cold and Flu Season? Why is this not happening throughout the year?

There are several factors that help promote the spread of viruses in the winter.

1. People spend more time indoors, in close proximity to one another, making it easier for the virus to spread from person to person.
2. In the Northern Hemisphere, increased travel during the holidays can increase the incidence of colds and flus.
3. Drier air and dehydration can prevent the body from expelling virus particles.
4. Viruses survive longer on surfaces when temperatures are colder, increasing the chance of transmission.

But it's not just the cold air and low humidity of winter that promotes viruses. Cold and Flu seasons occur in more tropical regions as well, during the rainy season - also a time when people spend more time indoors.

We've considered the external factors that can influence the cold and flu season, but there are other factors inside our body.

In the winter months, we have shorter days and less sunlight. We spend more time indoors, so even on a sunny day we rarely get exposure to the sun. Since our body uses sunlight to produce Vitamin D, in the winter months the Vitamin D levels in our body are at their lowest. People with the lowest levels of Vitamin D in their blood are the most likely to catch colds. Asthma patients have twice as many respiratory infections when they have a Vitamin D deficiency.

Dr. John Cannell has an excellent explanation on how Vitamin D affects the immune system, and prevents illness. See the video below:

It is interesting to note that viruses will attack your weakest cells, which are cells you probably want to eliminate anyway. When you blow your nose, all that mucous contains large quantities of dead cells that you are cleaning out of your system.

This explains why you are less likely to get a cold if you are in excellent health, but it also explains some benefit to getting some rest and letting a cold run its course.

Some people believe in taking antibiotics for a flu, they may get some relief from the antibiotic's anti-inflammatory effect, but antibiotics fight bacteria, not viruses, and so any positive effect may not be worth the negative impact on your digestive tract - which may lead to further weakening of your immune system, and more colds and flus.

Knowing the factors that contribute to the cold and flu season will help us prepare to minimize the impact, and reduce our 'sick days'.

We may be more likely to be exposed to these viruses in the winter, but if we keep our bodies strong, get in the sunshine whenever possible, and make sure we get plenty of Vitamin D, we reduce our risk of the illnesses associated with the season.