If only standard diagnostic criteria, most often presence of a fever, is used to identify H1N1 infection, it may not be enough, warns a recent study.
It has, therefore, concluded that coughing or other respiratory symptoms are more accurate in determining influenza infection than presence of a fever.
Currently, public health officials rely on body temperature (detecting fever) to screen individuals for potential infection with H1N1.
However, the study's authors found that coughing, not fever is a more reliable indicator of infection because nearly half of the individuals with mild infection may not have fever.
A team led by Sang Won Park of Seoul National University investigated confirmed cases of H1N1 who were hospitalized and quarantined during the early stages of the pandemic in 2009.
The study's results showed only 45.5 percent of the case subjects had fever. Individuals with mild infection and no fever have the potential to evade detection at airports or medical triage units, thus continuing the chain of infection.
"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," Park said.
"We are aware of other studies that show fever present in as few as 31 percent of confirmed cases of influenza. We found that the most sensitive indicator was cough.
Park added that that "screening should take any kind of respiratory manifestation into account."
The findings were published in American Journal of Infection Control, the official publication of the Association for Professionals in Infection Control and Epidemiology, (APIC).