Doctors shouldn't base an H1N1 influenza diagnosis on the fever symptom alone, as those with mild infections may not have a fever, according to new research published Thursday in the American Journal of Infection Control.

The researchers, led by Dr. Sang Won Park of Seoul National University, discovered that coughing or other respiratory symptoms are more accurate in determining influenza infection than the presence of a fever.

"Our study found that fever is not reliable for case definition, even though it has been regarded as a key factor in determining influenza infection," said Park in prepared remarks.
The researchers investigated lab-confirmed cases of H1N1 in patients who were hospitalized and quarantined during the 2009 pandemic and found that only 45.5 percent of the patients had a fever. Fever is a conventional screening tool for physicians because it is a common symptom in many influenza and influenza-like illnesses, says Allison Aiello, assistant professor of public health and epidemiology at the University of Michigan's School of Public Health. Aiello also sits on the editorial board of the American Journal of Infection Control.

"A lot of researchers have come to that realization that fever...is not a very good screening tool by itself for lab-confirmed H1N1 or seasonal flu cases," she told DOTmed News.

The researchers noted that during a pandemic, a standard screening tool at airport security relies on body temperature scanners to detect the presence of a fever. These findings indicate that those with a mild infection were able to evade security and pass the virus on to others.

"[This research] reminds us that flu outbreaks change from season to season and that we can't rely on one symptom alone to screen for potential lab-confirmed influenza cases," says Aiello. "We need to look at clusters of symptoms that are most associated with new strains and do that on a case-by-case basis."

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