There are many rapid laboratory tests for diagnosing infections, but most of them are non-specific for infectious pathogens. To resolve this issue, we supposed that the degree of neutrophil activation (granulation, vacuolation, and increase in nucleic acids) is related to infectious pathogens. So we used routine hematological assays to measure the degree ofneutrophil activation in 68 patients (38 of whom were infected by influenza virus type A and 30 with bacteremia) and 23 healthy individuals. Results showed that the bacteremic group had significantly higher amounts of nucleic acids than did the influenza virus type A-infectedgroup (p<0.005). Therefore, our method could be a novel solution to differentiate between viralinfection and bacteremia. (FJJM 2011; 9 (1): 1-6)