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Cold and flu symptoms

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How to tell them apart

Colds and influenza (the flu) are both caused by viruses. Although they share many of the same symptoms, there are some key differences.

  • Colds can occur throughout the year. The flu generally infects people from late fall through early spring.
  • The symptoms of a cold include a stuffy or runny nose, sneezing, sore throat, mild fatigue, headache, and a cough.
  • Flu symptoms are usually more severe than those of a cold and tend to come on suddenly. They can include fever (100.4 degrees F or higher), fatigue (very tired), muscle or body aches, headache, chills, sore throat, cough, and a stuffy or runny nose. Some people may have vomiting and diarrhea, but this is more common in children than adults.
  • People who have the flu may be able to infect others from 1 day before getting sick until 5 to 7 days after. Young children and people with weakened immune systems can be infectious even longer.
  • An annual flu shot can help prevent or reduce the severity of illness caused by flu viruses. There are no vaccines for cold viruses.
  • The flu is more serious than a cold. According to the CDC, every year in the United States:
    • Up to 20 percent of Americans (1 in 5 people) get the seasonal flu.
    • More than 200,000 people are hospitalized from seasonal flu complications, including 20,000 children.
    • Up to 36,000 people die from the flu every year.

Woman blowing her noseLearn more about respiratory infections in adolescents and adults and children

Related conditions

Nasal allergy symptoms ("hay fever") are much like those of a cold but aren't caused by a viral infection. An allergic response is your immune system's overreaction to particles in the air such as pollen, dust, molds, or pet fur and dander. Symptoms include clear mucus from the nose, sneezing, headache, watery eyes, dark circles under the eyes, irritability, fatigue, and a stuffy, runny, or itchy nose. Allergies can last weeks, months, or even years. Learn more about allergy symptoms and treatment.

Like allergies, there are other conditions that mimic cold and flu symptoms, or that occur if an infection develops in the ears, sinuses, chest, or other parts of the respiratory system including:

Bronchitis (chest cold)
Ear infections
Pneumonia
Sinusitis (sinus infection)
Strep throat

Reviewed by: Randy Bergen, MD, August 2013

Additional Kaiser Permanente reviewers

© 2011 Kaiser Permanente

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Get the facts

Is it a cold or the flu?

Although they have a lot in common, there are some key differences. How to tell them apart.