It’s that season again, either you have been sick, or you know someone who is ill. Flu season typically occurs during the winter months. So what are the differences between the flu and a common cold? What would make you suspect the flu?
Two of the most common viral respiratory infections, the common cold and influenza (flu), are often confused with each other because they share overlapping symptoms, such as cough, sore throat, and congestion. They are also both spread by respiratory droplets, close personal contact, and touching contaminated surfaces.
Despite these similarities, the common cold and influenza are distinct illnesses with important differences in cause, severity, complications, and prevention.
The common cold can be caused by many different viruses, with rhinoviruses being the most common culprits. Because so many viruses can cause colds, people can experience multiple colds per year.
Influenza, by contrast, is caused specifically by the influenza virus, most commonly influenza A and B strains that circulate seasonally. Influenza viruses are prone to frequent genetic changes, which is why new strains emerge regularly and why annual flu vaccination is necessary.
The common cold typically has a gradual onset of symptoms over a couple of days with a runny nose, sneezing, sore throat, mild cough, and fatigue. Sometimes accompanied by a low-grade fever, but not always.
Influenza presentation is more rapid with a sudden onset of systemic symptoms that are usually more intense and include fever often higher than 101°F, chills, severe fatigue, headache, muscle and body aches, dry cough, and sore throat. Nasal congestion is less prominent in influenza.
The duration of symptoms is usually longer with the flu than with a cold. The acute symptoms of the flu can last 7 to 10 days, with fatigue and weakness persisting for several weeks in some cases. The longer recovery time reflects the flu’s greater systemic impact on the body.
The biggest distinction between the common cold and flu is the potential for serious complications in the case of the flu. Influenza can cause severe and life-threatening complications, particularly in high-risk populations such as adults aged 65 and older,young children, pregnant women, people with chronic disease, or immunocompromised patients.
These complications include pneumonia, respiratory failure, myocarditis, encephalitis, sepsis, and death. Each year, hundreds of thousands of people in the US get admitted to a hospital for treatment, and many thousands die.
The common cold is typically diagnosed based on symptoms alone, but if the symptoms are more severe and influenza is suspected, a rapid diagnostic swab can be performed to confirm influenza. An accurate diagnosis of influenza is important because antiviral medications are available for influenza but not the common cold.
Unfortunately, there is no cure for the common cold, but symptomatic treatment can help with rest, fluids, decongestants, and acetaminophen or NSAIDs for discomfort.
In the case of influenza, antiviral medications such as oseltamivir (Tamiflu), if started within 48 hours of onset, can reduce symptom duration and lower the risk of complications.
Prevention strategies for the common cold include hand hygiene, avoiding close contact with sick people, and cleaning frequently touched surfaces. There is no vaccine for the common cold because there are so many different viruses that cause colds.
Fortunately, we do have vaccines for the flu. So in addition to the preventative measures we have in place for colds, vaccines are an effective way to reduce flu severity, complications, and transmission. Everyone without contraindications, age 6 months or over, should receive an annual flu immunization.
References:
Eccles, Ron. Understanding the symptoms of the common cold and influenza
The Lancet Infectious Diseases, Volume 5, Issue 11, 718 – 725 available at https://www.thelancet.com/journals/laninf/article/PIIS147330990570270X/fulltext?utm.
Gaitonde, D.Y., Moore, F.C. and Morgan, M.K. (2019) ‘Influenza: diagnosis and treatment’, American Family Physician, 100(12), pp. 751–758. Available at https://www.aafp.org/pubs/afp/issues/2019/1215/p751.html
Reinhart, K., Huang, S., Kniss, K., Reed, C. and Budd, A. (2025) ‘Influenza-associated pediatric deaths United States, 2024–25 influenza season’, Morbidity and Mortality Weekly Report (MMWR), 74(36), pp. 565–569. Available at https://www.cdc.gov/mmwr/volumes/74/wr/mm7436a2.htm?utm.
