South Korean researchers have found that individuals with mild H1N1 infection may go undetected using standard diagnostic criteria. The study, published in the American Journal of Infection Control, concludes that coughing and other respiratory symptoms are more accurate in determining H1N1 infection than the presence of fever.

Public health officials currently rely on body temperature (detecting fever) to screen individuals for potential H1N1 infection. The researchers, however, found that coughing is a more reliable indicator of infection because nearly half of the individuals with mild infection may not have fever.

The study looked at patients with confirmed cases of H1N1 who were hospitalized and quarantined during the early stages of the pandemic in 2009. The findings showed only 45.5% of the case subjects had 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 Sang Won Park, MD, professor at the Seoul National University. “We are aware of other studies that show fever present in as few as 31% of confirmed cases of influenza. We found that the most sensitive indicator was cough.”

Park adds that “screening should take any kind of respiratory manifestation into account.”

Source: Association of Professionals in Infection Control and Epidemiology