Symptoms of the flu
The flu attacks the nose, throat and lungs, but is different from a cold. Influenza usually comes on suddenly and may include fever, headache, extreme fatigue, dry cough, sore throat, nasal congestion and body aches which are sometimes severe.
Complications of the flu
Complications caused by the flu can result in very serious extended illness or even death in weakened individuals. Complications include bacterial pneumonia, dehydration and worsening of chronic medical conditions such as heart problems, asthma or diabetes. Children may get sinus problems and ear infections.
Each year, more than 200,000 people may be hospitalized from complications of the flu. Many thousands of people die each year from these complications.
How to Know if You Have the Flu
Your respiratory illness might be the flu if you have sudden onset of body aches, fever, and respiratory symptoms, and your illness occurs during November through April (the usual flu season in the Northern Hemisphere). However, during this time, other respiratory illnesses can cause similar symptoms and flu can be caught at any time of the year. It is impossible to tell for sure if you have the flu based on symptoms alone. Doctors can perform tests to see if you have the flu if you are in the first few days of your illness.
The myth of the "stomach flu"
Many people use the term "stomach flu" to describe illnesses with nausea, vomiting, or diarrhea. These symptoms can be caused by many different viruses, bacteria, or even parasites. While vomiting, diarrhea, and being nauseous or "sick to your stomach" can sometimes be related to the flu - particularly in children - these problems are rarely the main symptoms of influenza. The flu is a respiratory disease and not a stomach or intestinal disease.
How flu spreads
The flu spreads in respiratory droplets caused by coughing and sneezing. It usually spreads from person to person, though occasionally a person may become infected by touching something with virus on it and then touching their mouth or nose.
A person who is infected can spread the flu to others beginning a day or more before getting symptoms, and up to 7 days after getting sick. That means that you can give someone the flu before you know you're sick as well as while you are sick.