Flu is in general worse than the common cold, with symptoms that are typically more intense and begin more abruptly, while cold symptoms are usually milder, according to the Centers for Disease Control and Prevention. The agency says the two illnesses have similar symptoms, so it can be difficult to tell the difference between them based on symptoms alone. This page reports what the CDC states and is not personal medical advice.
How the CDC compares the symptoms
The CDC's page on the signs and symptoms of flu carries this comparison of a cold and flu:
| Sign or symptom | Cold | Flu |
|---|---|---|
| Symptom onset | Gradual | Abrupt |
| Fever | Rare | Common; lasts 3 to 4 days |
| Aches | Slight | Common; often severe |
| Chills | Uncommon | Fairly common |
| Fatigue, weakness | Sometimes | Usual |
| Sneezing | Common | Sometimes |
| Chest discomfort, cough | Mild to moderate; hacking cough | Common; can be severe |
| Stuffy nose | Common | Sometimes |
| Sore throat | Common | Sometimes |
| Headache | Rare | Common |
The agency's Cold Versus Flu page says people with colds are more likely to have a runny or stuffy nose than people who have flu. For the full list of flu symptoms and the emergency warning signs the CDC names, see What are the symptoms of the flu?
Different viruses cause them
The CDC says flu and the common cold are both contagious respiratory illnesses, but they are caused by different viruses. Flu is caused by influenza viruses only. The common cold can be caused by a number of different viruses, including rhinoviruses, parainfluenza and seasonal coronaviruses.
The agency's About Common Cold page says more than 200 respiratory viruses can cause colds, and that rhinoviruses are the most frequent cause of colds in the United States. The same page says the viruses that cause COVID-19, flu and RSV can also cause cold-like symptoms but do not cause colds, and that those viruses are more likely to cause severe illness.
What the CDC says about a cold
The CDC's About Common Cold page says colds usually last less than a week. It says the signs and symptoms of a cold usually peak within 2 to 3 days of infection and can include:
- Runny nose
- Nasal congestion
- Cough
- Sneezing
- Sore throat
- Headache
- Mild body aches
- Fever, which the page says is usually low grade in older children and adults
The same page says adults in the United States have an average of two to three colds every year, and children often have more.
How serious each one can be
The CDC's Cold Versus Flu page says colds generally do not result in serious health problems, such as pneumonia, bacterial infections or hospitalizations. It says flu can have serious associated complications.
For how long flu illness runs, see How long does the flu last? For when flu circulates, see When is flu season?
How flu is diagnosed
The CDC says special tests can tell if a person is sick with flu. Its page on flu diagnosis says testing is the only way to know if a person has flu, though a health care provider may diagnose flu based on symptoms.
That page says a number of tests are available to detect influenza viruses in respiratory specimens. It says rapid influenza diagnostic tests can provide results within approximately 10 to 15 minutes but may not be as accurate as other flu tests.
The CDC's About Common Cold page tells people who have cold-like symptoms and suspect they have COVID-19 or flu to get tested. For how much flu is circulating now, see Is flu and respiratory illness high in my state?