An average of 20,000 children under the age of 5 are hospitalized for complications resulting from the influenza virus each year, according to the U.S. Department of Health and Human Service. Children are more at risk for contracting the flu than adults and the majority of flu symptoms aren't exclusive to children. Learning to recognize symptoms early ensures swift, prompt treatment for your entire family.

Fever

A fever alone is not indicative of the flu. KidsHealth.org points out that a fever can occur even with the common cold. It's the nature of the fever that raises warning signs among concerned parents. A sudden onset of fever accompanied by chills is a strong indicator your child is coming down with the flu. Kids who have the flu can have a temperature over 100 degrees Fahrenheit, but may report feeling cold or have a moderate temperature. Watch your child for physical signs of a fever. In addition to taking her temperature, look for flushed, warm skin. Also, you can't assume that illness without a fever isn't the flu. The United States Centers for Disease Control and Prevention cautions that not everyone who comes down with the flu runs a fever. Since a fever can quickly rise to dangerous levels, seek medical attention as soon as possible if a fever persists and does not respond to treatment.

Respiratory System

The flu is a virus that primarily targets the respiratory system, according to MayoClinic.com. If you suspect your 3-year old has the flu, listen for a dry hacking cough. Watch your child for sniffling or frequent nose blowing – indicators that she has a runny or stuffy nose. A sore throat can accompany these respiratory systems, either as a direct symptom of the flu itself or as a result of post-nasal discharge from a runny nose.

Musculoskeletal System

Your child's activity level can suddenly decline at the rapid onset of the flu and he might report feeling more tired than usual. The CDC lists fatigue as one of the symptoms of the flu. If general tiredness is coupled with unpleasant muscle and body aches, your 3-year old may be experiencing the flu. Some kids with the flu experience headaches, which may be due to sinus congestion.

Gastrointestinal System

Kids experience gastrointestinal upset more frequently than adults, according to the CDC. Kids with the flu might vomit or experience diarrhea. These symptoms are usually caused by the virus itself, but may also be the result of excess phlegm and sputum. Diarrhea and vomiting can lead to dehydration, particularly in children. Speak to your doctor if your 3-year old is unable to keep down clear fluids when battling the flu.