There are over 200 different strains of “cold” viruses, mainly made up of rhinoviruses (up to 50%). The average american adult will get 2-4 colds per year. The average child will get 6-8. Most of the symptoms will be mild and up to 25% of infected people won’t show any symptoms at all. Most won’t get a fever, and if they do, it will be low-grade- around 100 degrees Fahrenheit. These viruses primarily won’t transmit through the air. Instead, people become infected by coming into direct contact with someone who has an infection, or touching something that an infected person touches.

If any given group of people were exposed to the same cold virus, many would have mild to no symptoms, and some would have more severe reactions. The same can be said for flu viruses. The distinction between the two also gets blurred by some people’s tendency to over-exaggerate their symptoms. In truth, a person’s reaction to them aside, these are two very different types of viruses.

Influenza affects approximately 10% of the US population every year. This virus tends to start with sudden onset of a higher fever between 100-104 degrees Fahrenheit. It then progresses into chills, headache, muscle aches and a loss of appetite. Flu’s can also lead to more serious conditions like bronchitis and pneumonia. Those whose immune systems might be compromised, like the elderly or chronically ill, are at risk of death. Approximately 20,000 people a year die from the flu.

There are several contributing factors to why cold temperatures increase influenza infection rates. The most common is that people tend to stay indoors when the temperatures get colder. This allows people to be in closer contact with each other and therefore makes it easier to pass the virus from person to person. Another contributing factor is that children are going back to school and interacting more with their fellow infected students. In fact, most epidemics can be traced back to children.

The reason flus are more common in the winter can be found in determining how this virus reacts to temperature and humidity. The virus is extremely stable in colder temperatures, 41 degrees Fahrenheit optimally. The warmer you go, the less stable it becomes. Around 86 degrees, the virus isn’t transmitted at all.

Humidity also plays a very important role. Influenza is primarily transmitted on the droplets from your respiratory tract. The more humid the environment, the more water is available for those droplets to “pick up”. The heavier the droplets become, the faster they will fall to the ground and out of the way of our mucus membranes. In drier environments, those death droplets hang around in the air longer for others to breathe in. In fact, one study showed that the virus was best transmitted at a humidity of 20% and not transmitted at all once the humidity reached 80%.