Influenza (Flu) In general, flu is worse than a cold, and symptoms are more intense. People with colds are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations. Flu can have very serious associated complications.
Flu can cause mild to severe illness, and at times can lead to death. Flu usually comes on suddenly. People who have flu often feel some or all of these symptoms:
Fever (common, but not always) or feeling feverish/chills
runny or stuffy nose
muscle or body aches
some people may have vomiting and diarrhea, though this is more common in children than adults.
Most people who get flu will recover in a few days to less than two weeks, but some people will develop complications (such as pneumonia) as a result of flu, some of which can be life- threatening and result in death. Sinus and ear infections are examples of moderate complications from flu, while pneumonia is a serious flu complication that can result from either influenza virus infection alone or from co- infection of flu virus and bacteria. Other possible serious complications triggered by flu can include inflammation of the heart (myocarditis), brain (encephalitis) or muscle (myositis, rhabdomyolysis) tissues, and multi-organ failure (for example, respiratory and kidney failure). Flu virus infection of the respiratory tract can trigger an extreme inflammatory response in the body and can lead to sepsis, the body’s life-threatening response to infection. Flu also can make chronic medical problems worse. For example, people with asthma may experience asthma attacks while they have flu.