The flu is highly contagious and within two to three weeks, it will have travelled amongst the people that you surround yourself with, with schools and the workplace being particularly troublesome when it comes to catching the illness. The flu also tends to last a little longer than the common cold, with people often getting over the cold within a week whereas the flu can stick around for up to two weeks.

If left untreated, both diseases can cause complications, but the flu is by far the worse. Flu cases can easily lead to death if not treated, since the virus is a lot more powerful and it is also more adaptable to avoiding medication and to countering the infected person’s immune system (actually, the flu virus is known to be one of the most "instinctive" and adaptable viruses of all time, since it constantly mutates into newer, better versions).

A case of flu can become deadly in many ways, either through high fever, reducing the immune system to a point where the body is easily afflicted by numerous other diseases, but most commonly, flu is deadly by causing an acute respiratory deficiency. On the other hand, it’s relatively hard for a common cold to become lethal. Even if left untreated by modern medication, a common cold can be naturally healed. And while the cold itself will almost never be the cause of death, the complications it can produce, such as pneumonia for example, may very well do so.

When it comes to keeping the illnesses at bay, your best bet is to exercise caution when it comes to being sanitary. When flu season strikes or someone around you has a cold, be sure to wash your hands often. 

Also, if you are a smoker, you may want to avoid the habit for a few days as it can prove to have a negative effect on your body’s ability to prevent respiratory illnesses.

Adequate rest is very important for both the flu and the common cold.  Drinking plenty of water is also very important as moist tissues are harder for a virus to infect than dry tissues.