Influenza Symptoms: The Flu, or Something Else

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Antiviral drugs can be effective in treating the flu, if they are started within the first 36 to 48 hours of infection. They have only modest benefit, if any, at treating other viruses which produce similar symptoms. Dr. Jonathan L. Temte and Dr. Jacob P. Prunuske of the University of Wisconsin School of Medicine and Public Health encouraged doctors to make a correct diagnosis before prescribing any of these drugs, because the side effects can be significant for some people.

Dr. Mark H. Ebell and Anna Afonso at The University of Georgia provided a review for physicians on how to diagnose influenza. These authors offered several motivations for accurate diagnosis, in addition to the decision about prescribing antiviral drugs. A correct diagnosis rules out other diagnoses, guides patient education, and lets the patient know what to expect.

It is not so easy, even for doctors, to diagnose influenza based solely on symptoms, Ebell and Afonso reported. The symptoms overlap those of other infections. Lab tests may be necessary. However, the most important symptoms are fever, cough, and acute onset (the illness develops quickly, over a period of a few days or less).

The Centers for Disease Control and Prevention lists possible influenza symptoms as follows:

1. Fever

2. Cough

3. Sore throat

4. Runny nose or stuffy nose

5. Muscle aches

6. Headache

7. Fatigue

8. Vomiting and diarrhea, more often in children than in adults.

Infected individuals often experience some or all of these. Complications of influenza include pneumonia, bronchitis, sinus infections, and ear infections, sometimes from secondary bacterial infections. Patients with complications experience more severe symptoms.

Dr. Barbara Michiels and colleagues at the University of Antwerp, Belgium, performed a study to see how many patients with flu symptoms actually have influenza. During five winter periods, 2002 to 2007, a group of general practitioners tested 4,597 patients with influenza-like illness. Overall, 52.6 percent actually had influenza.

So when you have flu symptoms, you may have influenza or you may have another infection. See your doctor for diagnosis.

References:

1. Temte JL et al, “Seasonal influenza in primary care settings: Review for primary care physicians”, Wisconsin Medical Journal 2010; 109(4): 193. http://www.ncbi.nlm.nih.gov/pubmed/20945720

2. Ebell MH et al, “A systematic review of clinical decision rules for the diagnosis of influenza”, Annals of Family Medicine 2011; 9(1): 69-77. http://www.ncbi.nlm.nih.gov/pubmed/21242564

3. Centers for Disease Control and Prevention. Seasonal Influenza (Flu). Influenza: The Disease. Web. August 10, 2011.
http://www.cdc.gov/flu/about/disease/symptoms.htm

4. Michiels B et al, “Clinical prediction rules combining signs, symptoms and epidemiological context to distinguish influenza from influenza-like illnesses in primary care: a cross sectional study”, BMC Family Practice 2011; 12: 4. http://www.ncbi.nlm.nih.gov/pubmed/21306610

Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.

Reviewed on August 25, 2011
by Maryann Gromisch
Edited by Jody Smith

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