Flu (Influenza) Symptoms

The flu (influenza) is contagious virus that affects the respiratory system. Even if the symptoms are mild, it can further complicate any previous medical conditions.

While flu symptoms are often very similar to cold symptoms, rarely do colds cause fever over 101ºF. Learning to recognize the difference so you can be prepared to take action if necessary will aid in faster recovery if you or someone in your family has the flu.

The three types of flu viruses are: Influenza A (can also be broken down into subtypes and even further into strains), Influenza B and Influenza C viruses. Influenza A and B viruses are the two main types which are responsible for seasonal flu epidemics annually.

Over the course of the flu season, types and subtypes of A and B viruses spread and cause seasonal epidemics. The viruses are also continually mutating through a process called "antigenic drift." Influenza C is thought not to cause epidemics.

• Fever
• Aches
• Chills
• Tiredness
• Sudden symptoms

Flu symptoms can be mild to severe — and if they are mild at the onset, it can suddenly change and become severe without notice.

• Fever (usually high)
• Headache
• Body and muscle aches
• Chills
• Extreme fatigue
• Dry cough
• Runny nose
• Stomach symptoms, such as nausea, vomiting, and diarrhea

All of the above symptoms do not have to be present to have the flu. If you have one or two, it's recommended that you see your doctor.

Flu cannot be diagnosed on symptoms alone so it is best to see a doctor if you think you might have the flu. A test can be conducted to determine if you have the flu or a complication of the flu.

People who are at high risk for complications of the flu include young children, persons with chronic medical conditions (diabetes, heart disease, asthma), pregnant women and people over 65 years of age.

If complications arise from the flu it can be serious especially for people with previous health conditions. It can cause bacterial pneumonia, heart failure, dehydration and even death.