Flu symptoms often start with a fever that comes on quickly, whereas cold symptoms typically begin slowly and are more likely to include a runny or stuffy nose. Flu symptoms tend to be more severe than those of a cold, with viral infection of the throat, nose, and lungs more likely to lead to a range of potentially serious complications, according to the Centers for Disease Control and Prevention (CDC).

What Are the Symptoms of a Common Cold?

Cold symptoms typically appear about one to three days after exposure to a cold-causing virus, with most cases peaking within two to three days.

ymptoms of a cold can include:

  • Runny or stuffy nose
  • Sneezing
  • Postnasal drip
  • Coughing
  • Sore throat
  • Watery eyes
  • Fever (most people with a cold will not have a fever)

What Are the Symptoms of the Flu?

Unlike cold symptoms, which develop gradually, flu symptoms usually come on suddenly. Cold and flu symptoms may overlap, but the latter tend to be more severe. There is also a greater risk of developing complications, such as pneumonia, in people who get influenza.

symptoms of the flu typically include:

  • Fever (but not everyone with the flu develops a fever)
  • Runny or stuffy nose
  • Coughing
  • Sore throat
  • Fatigue
  • Muscle or body aches
  • Headaches
  • Vomiting and diarrhea (more common in children)

The CDC lists a number of emergency warning signs that should prompt immediate medical attention, including:

  • Difficulty breathing or shortness of breath
  • Persistent pain or pressure in the chest or abdomen
  • Persistent confusion, dizziness, unconsciousness
  • Seizures
  • Not urinating
  • Severe muscle pain
  • Severe weakness or unsteadiness
  • Fever or cough that improves, then returns or worsens
  • Worsening of chronic medical conditions 

Source: https://www.everydayhealth.com/flu/guide/symptoms/