CRP and influenza: CRP can be used to assist with differentiation between viral and bacterial infections, for example, influenza produces a mean CRP level of 25.65 mg/L [95% confidence interval (CI) 18.88 to 32.41 mg/L] versus bacterial pneumonia which produces a mean CRP level of 135.96 mg/L (95% CI 99.38 to 172.54 mg/L).4