What Are the First Signs of the Flu?

Sick woman on the couch
How does the flu start?. Cultura RM Exclusive/Colin Hawkins/Getty Images

When you get a cold or other upper respiratory infection, it usually starts out slowly. You may feel a headache, a mild sore or irritated throat, some congestion or any number of other cold symptoms. They start out mild and get worse after two to three days and then gradually go away.

That is not how the flu starts. The real flu - influenza - comes on suddenly and in full force. Most people feel completely normal when they go to bed and then wake up in the morning feeling like they were "hit by a truck".

A majority of people who have the flu will have a fever, body aches, headache and cough. Congestion is a symptom as well but is often not severe.

Contrary to popular belief, vomiting and diarrhea are not common symptoms of the flu. They are more common in children with influenza, but only occur in about 10% of people that have it. If your primary symptoms are vomiting and diarrhea, you most likely have a gastroenteritis - or stomach virus.  

What Else Should You Know?

Recognizing the symptoms of the flu early is essential if you want to try to treat it rather than just letting it run it's course. If you are in a high risk group, it's especially important to seek medical attention within the first 48 hours of the start of your symptoms. 

Antiviral medications such as Tamiflu and Relenza are available to help with the flu but are most effective if started within 48 hours of getting sick. These prescription medications can help shorten the duration of the illness and lessen the severity of the symptoms, meaning you won't feel quite as bad for quite as long as you would have if you didn't take it.

 

For people that are at high risk for complications from the flu - like young children, older adults and people with chronic health conditions, taking an antiviral medication could mean the difference between being hospitalized and being able to recover at home. They aren't a guarantee or a cure, but they do help many people.

 

When to Be Concerned

Some people will develop complications from the flu, such as pneumonia, bronchitis or even respiratory failure. In children especially, these warning signs can develop quickly. If you notice any of these symptoms, seek medical attention right away.

In children:

  • Difficulty breathing - including shallow, rapid breathing 
  • Bluish color to face or lips
  • Difficulty waking up or staying awake
  • Extreme irritability or unable to be consoled when crying
  • Signs of dehydration
  • Infants that have no tears when crying
  • Infants that are unable to eat or have significantly fewer wet diapers than normal

In adults:

  • Shortness of breath
  • Severe chest or stomach pain
  • Sudden dizziness or confusion
  • Severe vomiting that won't stop

If you or your child have flu symptoms for several days, start to feel better for a day or two and then symptoms return or worsen - typically with a higher fever - contact your health care provider. This is a sign that you have developed a secondary infection like pneumonia, which may need to be treated differently.

 

Sources:

"Flu Symptoms & Severity". Seasonal Influenza (Flu). 16 Sep 15. US Centers for Disease Control and Prevention. Department of Health and Human Services. National Institutes of Health. 25 Feb 16. 

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