Symptoms of Influenza

Flu symptoms can vary from person to person but most people with influenza will experience some, if not all, of the symptoms listed here. If you are concerned and think you might have the flu, contact your health care provider to determine the best course of action and treatment for you.

Symptoms of the flu are similar to those experienced when you have a cold or upper respiratory infection. The main difference is influenza symptoms come on rapidly. People typically go from feeling fine to miserable in a matter of hours. Here's a closer look at common symptoms.

Fever is almost always present with the flu, and it usually comes on suddenly. When you have a high fever, you're also likely to experience chills. The higher your body temperature, the colder the air will feel.

This is why you feel cold when you have a fever and why you want to cover up with blankets to get warm. Unfortunately, if you bundle up when you have a fever, you can actually increase your body temperature, which won't help you feel any better.

It's hard to get comfortable when you have a fever. You can use appropriate fever-reducing medications.

One of the most significant symptoms that people describe when they get the flu is pure exhaustion. This is generally an overall feeling of being completely worn out. You probably will be unable to perform daily activities. It's so severe that it is hard to get out of bed. This exhaustion is much more pronounced than the tiredness you may feel from a cold.

One of the most common descriptions people give when they have the flu is "achy." Your muscles are usually very sore and moving around too much causes discomfort. Body aches and pains are more common with the flu than with many other illnesses.

Coughing may be productive (producing mucus) or non-productive. With the flu people most often suffer from a dry cough.

If you develop a productive cough with fever, contact your doctor. This is especially true if you have had a dry cough, start to feel better, then have a wet or productive cough with a fever. This is often how a secondary infection, like pneumonia, develops.

Severe congestion is more common when you have a cold but many people will experience some congestion with the flu as well. It is typically mild.

Headaches are common with the flu and can be quite severe. Like the rest of your body, the head will ache when you have the flu.

Throbbing head pain can make you miserable when you already feel bad with the flu. Taking an OTC pain reliever like acetaminophen or ibuprofen may help.

Vomiting and diarrhea are not common flu symptoms for most people. However, some people do experience these symptoms with the actual flu.

Children are more likely to have vomiting and diarrhea with influenza, but they may occur occasionally in adults as well. About 10% of children have these symptoms with the flu. 

If vomiting and diarrhea are your primary and most significant symptoms, you probably have a stomach bug (sometimes referred to as the stomach flu), not influenza.

For most people, flu symptoms resolve in one to two weeks. However, some people are at higher risk of complications, which may be life-threatening. In fact, there are 20,000 to 60,000 deaths from influenza in the United States each year.

Complications from the flu range from mild sinus or ear infections to serious and life-threatening. Serious complications include: 

• Pneumonia
• Myocarditis, inflammation of the heart
• Encephalitis, swelling of the brain
• Multi-organ failure
• Sepsis
• Worsening of chronic medical conditions

If based on the symptoms, you believe you may have your flu, call your doctor right away. Antiviral medications, such as Tamiflu, can lessen the severity and duration of the flu if started within the first 48 hours of symptom onset.

Your doctor may want you to come in to confirm the influenza virus with a rapid in-office test or may prescribe solely based on your symptoms and flu activity in your area.

You should also contact your doctor if symptoms continue to worsen after a week with the flu or if once you start to feel better develop a fever or productive cough as influenza can turn into secondary infections, such as bronchitis and pneumonia.