by Daniel Choi

Created on: February 08, 2009

Both the flu and the common cold are highly contagious viral diseases. Both can be spread by aerosol transmission or by touch. In their earliest stages, they both have similar symptoms. In contrast to most viral infections, it is impossible to develop a permanent immunity either to the common cold or to the flu. However, they are caused by different viruses which have different structures and properties, and they develop in different ways.

The common cold is caused by either a piconavirus or a coronavirus. The immunological reaction to this virus is what causes the classic runny nose and scratchy throat of the common cold. Colds usually run their course in a few days.

The flu is caused by either the influenza A, B, or C genus of viruses. Each of these genera are divided into multiple serotypes and strains, with new strains arising every year. Flu symptoms will generally express much more suddenly and with greater severity than cold symptoms. The flu usually runs its course in 1-2 weeks.

The early symptoms for both the common cold and the flu are congestion, sneezing, and coughing. Both sneezing and coughing are ways for the body to expel excess mucus. Congestion can be present in the sinuses, throat, or lungs for both the cold and the flu. However, stuffy sinuses are usually indicative of a cold, while chest congestion is more typical of the flu. This is why sneezing is much more typical of colds, and coughing of flu. Dry coughing in particular is almost always symptomatic of flu, and may also indicate the onset of bronchitis. For the same reason, chest discomfort is usually indicative of flu.

Three other shared symptoms are head and muscle aches, fever, and lethargy, which are caused by the body's immunological response. These are much more severe with the flu than with the common cold. In particular, headache and muscle pain may not even present with a common cold. Where there is no reason to suspect anything other than flu or cold, fever combined with chills nearly always indicates the flu. Sudden fever combined with headache or widespread bodily ache, in conjunction with congestion and coughing, are primary symptoms for diagnosing flu.

A dry, scratchy throat is a primary symptom of the common cold, and usually presents at the same time as the runny nose. With the flu, a sore throat presents much later, and is usually indicative of a secondary infection such as staph. In case of doubt, a throat swab can usually clarify whether a secondary infection is responsible.

Nausea

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