Influenza (Flu) or Common Cold? Here’s How To Tell

Influenza and the common cold are both viral respiratory illnesses. Out of the two, the latter occurs most often. In fact, it accounts for about one billion cases per year.

The flu is caused by one of three types of influenza virus: A, B, or C. On the other hand, the common cold is caused by over 250 viruses. Rhinoviruses — which makes up 40 percent of all cases — and coronaviruses are the most common etiologies.

Most cases of both the flu and the common cold are self-limiting. Self-limiting means that they resolve on their own. However, both can give rise to complications of a bacterial nature. This includes:

Unfortunately, both viral illnesses are responsible for a significant number of missed school and workdays, which speaks to their economic impact.

How Do You Know If You Have Flu or Cold Symptoms?

Because the flu and the common cold share so many symptoms, it can be very difficult to tell which one you have been unfortunate enough to contract. In general, the flu has more intense signs and symptoms when compared to the common cold.

The table below highlights some of the pertinent differences between the flu and the common cold.

Signs and SymptomsFluCommon Cold
SeasonLate October to March Year round, but winter and spring predominate
Symptom OnsetQuick; within hoursGradual; over several days
Fever Usually and high (101 °F to 104 °F) and can last three to four days Rarely and usually low-grade (greater than 98.6 °F but less than or equal to 100.4 °F)
ChillsFairly commonUncommon
Muscle/Body AchesCommon and can be severeMild
FatigueModerate to severe and can linger for two to three weeks or moreUsually mild
Nasal Congestion (“Stuffy Nose”)SometimesCommon
Runny NoseSometimesCommon
Sore ThroatSometimesCommon
HeadacheCommon and can be severeSometimes and usually mild
CoughTypically, dry and nonproductiveTypically, productive of mucus, which can be clear, yellow, or green
Chest DiscomfortCommon and usually severeSometimes and usually mild
DiarrheaSometimes and occurs more often in children than adultsNo
ComplicationsPneumonia, which can be life threateningAcute bronchitis, acute bacterial sinusitis, and acute otitis media
PreventionAnnual vaccination; best if received by the end of OctoberFrequent hand washing
TreatmentAntiviral medication, oseltamivir or baloxavir, within 24 and 48 hours of onset of symptomsSymptomatic relief, including hydration, rest, non-steroidal anti-inflammatory drugs, cough suppressants, decongestants, antihistamines, vitamin C, echinacea, and zinc

When to See a Doctor

Most individuals with the flu or the common cold won’t need to see a doctor.

If you suspect that you have the flu and are a member of a high-risk group, you should see a doctor. High-risk groups include those:

  • Under the age of five or over the age of 65;
  • Are pregnant, or;
  • Who have a weakened immune system or a chronic medical condition, such as diabetes or heart disease.

Antiviral medications prescribed within 48 hours of the onset of flu symptoms have the potential to shorten the duration of symptoms by one to two days. Additionally, they can potentially prevent or decrease complications.

The common cold with mild to moderate symptoms typically responds well to over-the-counter medications for symptomatic relief. However, you may want to visit your doctor for severe symptoms to make sure nothing more sinister is brewing.

Other reasons to see a doctor when you have the flu or common cold include:

  • No significant improvement in symptoms after two to three weeks;
  • Persistent fever or its sudden return after obvious resolution;
  • Persistent chest discomfort or cough;
  • Shortness of breath, and;
  • Increasing pain in an area such as the ears, sinuses, or throat.


Most individuals who are unlucky enough to contract the flu or the common cold will reclaim their health in a week or two. Although the flu is worse than the common cold, both have the potential to make you miserable.

The best prevention for the flu is a yearly vaccination, while the best prevention for the common cold is frequent hand washing.

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Oct 21, 2019