We often refer to this time of year as "cold and flu season." These illnesses often get lumped together, but there are important similarities and differences you need to know.
What's a cold?
The "common cold" is not one disease, but a group of viruses with relatively similar symptoms. Rhinovirus, adenovirus, and coronavirus are some of the most common, but in total over 200 different viruses can cause a cold. Each virus can vary in duration and severity, but the main symptoms are generally the same – runny nose, nasal congestion, coughing, sneezing, fever, headache, and body aches.
What's the flu?
Influenza, "the flu", is also caused by a virus. Every year, new flu strains develop and spread around the world in waves. Most flu outbreaks are relatively minor, but major epidemics can occur. Even though the flu is mostly just a nuisance, it can occasionally cause major problems, especially in older people.
What's the difference?
Both colds and flu are most common in the late fall, winter, and early spring. The viruses can be transmitted from one person to another by contact or by airborne droplets from coughing or sneezing. Also, many of the symptoms (such as coughing, chest congestion) are the same.
However, although colds and flu can cause the same general symptoms, the pattern of symptoms is generally very different. Colds usually cause a lot of upper respiratory symptoms (nasal congestion, coughing, runny nose) with little fever or body aches; the flu usually causes a prominent fever and body aches with relatively mild nose or throat symptoms. In addition, colds often take a few days from the first symptoms to the peak of maximum severity, but flu can go from first to worst in just a few hours.
Why does it matter?
There are no medicines that can really cure a cold, so the treatment is mainly focused on reducing symptoms with things like cough medicine, throat lozenges, and "grandma's chicken soup." Sometimes doctors give patients antibiotics for a cold just to "do something", but this is a bad idea and can only make things worse.
In contrast, there is treatment for the flu. A number of medicines are now available (such as oseltamivir/Tamiflu) that can shorten the course of the illness. In addition, there is a vaccine for influenza that can lower your chance of getting the flu. However, the flu vaccine does not do anything to prevent any of the viruses that cause colds.
What should you do?
First of all, make sure to get a flu shot every year. The best time is usually early fall, but any time in the fall or winter is worthwhile.
Second, if you think you have the flu, let your doctor know right away. The treatment is most effective the earlier you start it; once the flu has been going for a few days, the treatment is much less effective.