Cold vs. Flu

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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Cold vs. flu facts

  • The common cold and flu share many symptoms, and it can be difficult or sometimes impossible to tell the difference based on symptoms alone. Medical tests can identify the flu.
  • A cold and the flu are both caused by viruses, but these viruses are different. Flu viruses are far more capable of causing more harm to the patient than cold viruses.
  • The flu and the common cold are both respiratory illnesses; flu can be far more serious and may cause significant problems in the respiratory system.
  • Symptoms of the common cold versus the flu may be distinguishable in a number of patients.

What is the common cold?

The common cold is a viral infection of the upper respiratory system (nose, throat, sinuses, Eustachian tubes, trachea, larynx, and bronchial tubes). About 30%-50% of colds are caused by rhinoviruses; however, more than 200 different viruses may cause the common cold. Colds are contagious and can be transmitted from person to person. Colds have an incubation period of about one to seven days (time from infection to appearance of symptoms). A cold's duration (how long it lasts) is about seven to 10 days; however, depending upon the viral strain, it can last up to two weeks. Colds are considered mainly to be a mild respiratory illness.

What is influenza?

Influenza (commonly termed the flu) is a viral infection of the upper respiratory and/or lower respiratory system caused by influenza viruses. These viruses usually cause more serious symptoms in the respiratory system than cold-causing viruses. The flu is contagious, can be transmitted from person to person, and has an incubation period of about one to four days. The flu's duration varies from about five days to two weeks depending upon the severity of the infection. The flu can become an intense and potentially fatal illness in some individuals.

Cold & Flu Quiz: Test Your Medical IQ
Cough is a common symptom of a cold or the flu.

Cold, Flu, and Allergy Treatments

Millions of people use over-the-counter (OTC) products to relieve symptoms of cold, flu, and allergy, including nasal stuffiness and congestion, sneezing, runny noses, sore throat, and cough. The common causes of these symptoms include the viruses that cause the common cold, influenza virus, allergic rhinitis (hay fever), and sinus infections (sinusitis). Viral infections can also cause headache, body aches, fatigue, and sometimes fever. Hay fever symptoms can also include itchy eyes, nose, and throat, and watery eyes.

To benefit from OTC products for cold, flu, and allergy, it is important to understand (1) the condition causing the symptoms, (2) the predominant symptom(s) one wishes to relieve, and (3) the active ingredient(s) in the product. Some OTC products contain a single active ingredient medication to relieve one symptom. Many others contain a combination of two, three, and even four active ingredient medications to treat several symptoms at once. Selecting the right product can be difficult at times.

What are causes and risk factors of a cold and the flu?

The causes of the flu are mainly influenza viruses belonging to either influenza A or influenza B types of viruses. The causes of colds are usually rhinoviruses, but over 200 types of viruses are capable of causing the common cold. Risk factors for the common cold and flu are similar or identical. Risk factors include the following:

  • Contact with a person who has either a cold or the flu -- especially contact with mucus membranes, saliva, and/or items that an infected person has touched (for example, towels, toothbrushes, and cups)
  • Contact with other objects that may be touched by an infected person such as handrails, doorknobs, and other high-use items
  • Risk is increased in individuals with compromised immune systems.
  • In general, the young and the old are usually more susceptible to these viruses.
  • Stress, smoking, and lack of sleep can increase your risk for getting these viral infections.
  • Individuals who do not receive the yearly flu vaccine are more likely to risk getting infected with a flu virus; unfortunately, because of the huge number of viruses that may cause a cold, there is no vaccine available commercially against the cold viruses.

How can someone tell the difference between the cold and the flu?

As stated previously, sometimes it's difficult, especially in the early stages of infection, to tell the difference between a cold and the flu. However, there are some symptoms, if present, that may help distinguish between colds and the flu. They are summarized in the chart below.

Chart Comparing Cold vs. Flu Symptoms and Signs
SymptomsColdFlu
Fever (and/or chills)RareMild to high
Body/muscle aches and painsOccasionally, mildUsually moderate to severe
HeadacheUnusualUsually moderate to severe
CoughMild to moderateModerate to severe
Fatigue/weaknessMild to moderateUsually moderate to severe
Sore throatUsuallyUsually
Runny and/or stuffy noseUsuallyOn occasion
SneezingUsuallyOn occasion
Vomiting/diarrheaRareOccasionally
Abrupt onset of symptomsGradual onsetSometimes within three to six hours
Severity of symptomsMildModerate to severe

The above table shows the difficulty in diagnosing colds vs. flu using only symptoms; the best way is to do a short test for flu viruses done by trained medical caregivers.

What are the signs and symptoms of a cold and the flu?

The signs and symptoms of a cold or the flu are outlined in the table above. The flu symptoms are usually more intense than those seen in colds (moderate to severe) and can come on quickly after exposure to the viruses that cause the flu (for example, the swine flu virus strains). In addition, colds don't typically cause death, but the flu is noted to cause death due to respiratory failure in some people.

When should I call the doctor about my cold or the flu?

If a person develops trouble breathing, has a severe sore throat, has a cough that produces green-colored mucus, has chest pain, or develops a high and persistent fever, that person should be seen by their doctor. If you suspect you have the flu and are pregnant, are over 50, have a weakened immune system for any reason, or have ongoing medical problems such as diabetes, you are at higher risk for developing complications due to the flu and should contact your physician. If you have a child under 2 years of age or have a friend or relative living in long-term care facility with flu-like symptoms, their doctors need to be notified.

How do health care professionals diagnose a cold and/or the flu?

Generally, health care professionals distinguish between the cold and the flu by running a rapid influenza diagnostic test, usually done within about 30 minutes. Depending on which test is used, the results can vary but most health care practitioners, including emergency medicine personnel, utilize this test. If the test is negative, patients probably have a cold unless their symptoms and signs become more severe.

What are treatments, medicines, and home remedies for the common cold and the flu?

Treatment options, medicines, and home remedies for the common cold and flu are almost exactly the same except for a few items that pertain to the more severe disease, the flu.

  • Common treatments for both diseases include rest and treatment of symptoms as they occur; fever is treated with acetaminophen. Symptoms can be managed with good hydration and over-the-counter cold/flu medications that include suppression of symptoms such as cough, congestion, nausea, and sore throat.
  • Medicines are usually over-the-counter cold/flu treatments that often are combinations of several drugs like acetaminophen (Tylenol), ibuprofen (Motrin), various cough suppressants, and/or decongestants; for the flu, some health care providers use drugs of the antiviral/neuraminidase inhibitor class (oseltamivir, peramivir, and zanamivir), especially in severe infections.
  • Home remedies for colds and the flu are similar; vitamin C, zinc, humidified air, steamy showers, gargling with saltwater, compresses to relieve sinus congestion and/or headaches, honey and lemon, ginger, and many other items have been recommended. It is best to check with your physician, especially if you have the flu, before relying on home remedies -- the home remedies mainly reduce symptoms but do not cure the diseases.
Cold & Flu Quiz: Test Your Medical IQ

What is the prognosis for the common cold and the flu?

In most individuals, the prognosis for the common cold and the flu are good to excellent. However, individuals with moderate to severe flu may have a fair to poor prognosis, depending upon how quickly the patient is diagnosed and treated. The poor prognosis for some severe flu infections is usually due to respiratory problems that become complicated to treat (for example, pneumonia) and may require hospitalization in an intensive care unit (ICU).

Is it possible to prevent the common cold or the flu?

Yes, it is possible to prevent the common cold or the flu, but it is not easy to do so if you live in crowded conditions where it's almost impossible to constantly avoid contact with any items touched by individuals with a common cold or the flu. The ways to prevent (or more realistically, reduce the chance of getting) the common cold and/or the flu are essentially the same. Strict hand washing and avoiding close contact with infected individuals and/or the items they touch is the most effective way to prevent or reduce the chance of infection with the viruses that cause these diseases. Vaccination with the yearly updated flu vaccine is another way to prevent or reduce the chance of infection with influenza viruses. Unfortunately, there is no vaccine against the 200-plus virus types that cause the common cold.

REFERENCE:

United States. Centers for Disease Control and Prevention. "Cold Versus Flu." Aug. 11, 2016. <https://www.cdc.gov/flu/about/qa/coldflu.htm>.

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Reviewed on 9/18/2017
References
REFERENCE:

United States. Centers for Disease Control and Prevention. "Cold Versus Flu." Aug. 11, 2016. <https://www.cdc.gov/flu/about/qa/coldflu.htm>.

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