Why colds and flu are more common in the winter

The cold and flu season has officially arrived.  Every year, with the beginning of fall and on into winter, the odds of us catching a cold or the flu, increase much more so than in the spring or summer.  But why is that?  Feeling sick and miserable with a cold or the flu is no fun any time of year but especially during cold weather when we are already cooped up inside for longer periods of time than ever. 

Distinguishing between a cold and the flu

To understand fully why we get sick more frequently in chilly weather it is important to know the difference between the common cold and the flu.  The viruses that cause each do not necessarily behave in the same way.

The common cold usually has the following symptoms:

·      Sore throat

·      Blocked, stuffy, or runny nose

·      Cough

·      Fever uncommon in adults but children are more likely to have one with a cold

Here are common symptoms of the flu:

·      Symptoms usually come on quickly

·      Sore throat

·      Fever which can be high

·      Headache

·      Muscle aches and soreness

·      Congestion

·      Cough

·      Little to no appetite

Colds are a more mild respiratory illness than the flu.  Cold symptoms can make you feel bad for a few days whereas flu symptoms can make you feel quite ill for a few days to several weeks.  The flu can also result in serious health problems such as pneumonia and hospitalizations.  Most colds will tend to go away by themselves but every year, the flu kills an estimated 250,000 to 500,000 people worldwide.

Why the increase in colds and flu in colder months?

There are several reasons researchers believe to be why colds and flu strike more often in the fall and winter:

·      Blame it on the cold air

Few of us relish being out in cold air and neither do cold or flu viruses.  The main way these viruses gain entry into our bodies is through our noses.  Our noses know this and that is why our nasal lining has built-in defense mechanisms to keep these microbial intruders out. To prevent these intruders invading our body, our noses constantly secrete mucus trapping the viruses which then are moved by tiny hairs called cilia lining out nasal passages.  As they travel down this passage, we swallow the viruses and our stomach acids neutralize the microbes.

But when the air is cold this cools the nasal passage and slows down mucus clearance.  Suddenly, the viruses can stick around longer making it easier to get inside of us.  Rhinoviruses which cause most colds actually prefer cold temperatures, which don’t help us out in succumbing to catching a cold.  This virus is also better able to reproduce at temperatures just below the body’s 98.6 degrees Fahrenheit. 

·      Low levels of vitamin D

Many of us routinely fall short of our intake of adequate vitamin D.  Most adults require about 600 IU (International units) of vitamin D per day while adults 70 and older are advised to increase their intake to 800 IUs each day.

The sunshine vitamin has been suggested as a possible nutrient that can help prevent disease including colds and flu. Part of the blame for an increase in colds and flu during the winter is the fact there are fewer sunny days that help improve our chance of making vitamin D.  Past studies have shown that vitamin D supplementation did show a modest protective effect in reducing the risk of infection from colds or flu by about 10 percent.  Individuals with the lowest vitamin D levels experienced the greatest benefit from supplementation. 

Best food sources of vitamin D include fatty fish such as sardines, salmon, or tuna.  Fortified foods such as milk are another good source of this fat-soluble vitamin.

·      Frequent time spent indoors

Once the weather turns cold, we will find ourselves spending more time inside.  The time spent in enclosed spaces, especially with other people nearby, the greater likelihood for
“catching” viruses from others who are carriers.  Children are particularly notorious for being disseminators of viruses.  We often are in much closer contact with small children – we carry them, hold their hands – and the fact they tend to be less hygienic.  Before we know it, we’ve picked up their cold or flu.