If you think you might have the flu, it's important to get a flu vaccine as soon as possible. However, if you're still not sure whether or not you have the flu, there are some other ways to determine whether or not you have an upper respiratory infection (URI). One way to detect an early stage of URI is by checking for signs and symptoms.

The most common signs and symptoms of URI are: fever, cough, sore throat, body aches, headache, and fatigue. If you experience any of these signs or symptoms, it's important to visit your doctor as soon as possible. 

Another way to detect an early stage of URI is by using a home test kit. These kits can be purchased online or in stores and will indicate whether or not you have the flu based on the results.