What's the difference between colds and the flu? A typical cold causes a runny nose (the discharge is usually clear, but it could be yellow or green), body aches, coughing, and sometimes a mild fever. By day four or five, you should be well on your way to recovery.
Flu, on the other hand, can produce all those symptoms, plus headaches, fatigue, and most significantly a fever of 100 degrees or higher.
Colds and flu are both caused by viruses, not bacteria, so it's really just time that will make them go away. That said, both ailments can morph into more serious conditions, including sinus infection, bronchitis, pneumonia, and strep throat.
How to tell? Go to the clinic if you have sinus pressure or pain, a persistent or worsening sore throat, a deep cough that's making you hack up yellow or green phlegm, fast or difficult breathing, ear pain, or a high fever. If you think you have the flu -- and it's diagnosed quickly enough, a health care provider can give you an antiviral drug to help ease symptoms faster.
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