Flu Symptoms: How To Tell If You Have The Flu

01/11/2013 08:20 am ET | Updated Jan 11, 2013

With news spreading that this year's flu virus may be more severe than in years past, it's understandable to feel some anxiety. In fact, the CDC is reporting that 29 states are experiencing a more widespread and virulent flu than last year's strain, though doctors suggest that the actual strains are not so different from each other.

“Reports of influenza-like-illness (ILI) are nearing what have been peak levels during moderately severe seasons,” Dr. Joe Bresee, Chief of the Epidemiology and Prevention Branch in CDC’s Influenza Division, said in a statement. “While we can’t say for certain how severe this season will be, we can say that a lot of people are getting sick with influenza and we are getting reports of severe illness and hospitalizations."

The measure used by the CDC to determine prevalence of ILI is based on reports from a sample of around 3,000 health care providers of how many patients are visiting them with flu-like symptoms. So far, about 5.6 percent of Americans have come in with some type of flu symptom. As Slate points out, that's fewer than the six percent who appeared in doctors' offices during the 2007/2008 season and definitely fewer than the 7.7 percent of those who appeared at doctor's offices during 2009's H1N1 "swine flu" pandemic.

It's important to look closely at that metric: people with symptoms that could be attributed to flu, who went to the doctor. Higher numbers may indicate a more widespread virus -- or more widespread concern over the virus, leading to more hospital visits. ILI is also not the same as confirmed flu cases -- many of the symptoms that can indicate flu could also be signs of a cold or another type of virus.

"Think of the flu as a respiratory infection that causes systemic effects," explains Dr. Travis Stork, ER physician and co-host of "The Doctors." "In addition to a dry cough you can also have fever, body aches, chills, and a headache. The flu can make you feel miserable 'all over' and in some cases, can lead to serious illness in susceptible individuals. A cold on the other hand is a localized upper respiratory infection primarily with symptoms from the neck up."

With that in mind, what are the symptoms of flu? And when is it time to see the doctor?

The flu virus is a respiratory illness and can cause many of the symptoms that everyone has experienced at one time or another: fever, body aches, coughing, congestion and fatigue. Most of the symptoms that are caused by the flu virus could also just as easily be the result of a cold virus infection, according to the CDC.

Some differences: the flu virus is more likely to cause fever -- and a higher fever, at that. Flu sufferers have more severe symptoms overall and are more likely to face fatigue, body aches and a dry cough. Cold sufferers, by contrast, more commonly have a stuffed or runny nose and respiratory congestion. Some flu sufferers also have intestinal symptoms, such as vomiting or diarrhea.

Despite concerns about the gravity of illness, the truth is that most flu cases are mild and do not require treatment or hospitalization. Flu, unlike cold, can in rare instances lead to serious conditions like pneumonia and bronchitis, and it can even lead to death in vulnerable populations. People with a higher than average risk for complications include children under five years, pregnant women, those with compromised immune systems and senior citizens. Asthmatics, those with blood disorders, congestive heart failure and even those who are morbidly obese are also at greater risk, according to the CDC.

If you're in one of the high-risk groups listed by the CDC (check here), it may be a good idea to check with a healthcare professional if you begin to experience flu-like symptoms.

"Reasons to visit the ER include severe dehydration, lethargy, confusion, or any other truly concerning symptom," Stork says. "What seems like the flu is not always the flu and vice versa and sometimes a visit to the ER is needed to properly diagnose and treat."

Watch The Doctor's discuss the cold vs. the flu in this clip:

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