The sensitivity, specificity, positive predictive (PPV) and negative predictive values (NPV) of CRP>5 mg/ml for bacterial mono-infection versus viral infections were 87.8% (CI95%: 78.2–94.3%), 30.8% (CI95%: 22.3–40.5%), 46.8% (CI95%: 38.3–55.4%) and 78.6% (CI95%: 63.2–89.7%), respectively. The gene discussed is CRP; the disease is infection.