The present invention provides a method of identifying meningitis as either bacterial meningitis or aseptic meningitis in a subject, comprising: a) measuring the amount of complement C3, complement factor B, complement membrane attack complex (MAC) protein, complement C5b, complement C6, complement C7, complement C8, and / or complement C9 in a cerebrospinal fluid (CSF) sample obtained from the subject; and b) comparing the amount of complement C3, complement factor B, complement MAC protein, complement C5b, complement C6, complement C7, complement C8, and / or complement C9 measured in (a) with the amount of complement C3, complement factor B, complement MAC protein, complement C5b, complement C6, complement C7, complement C8, and / or complement C9 measured in a control sample, wherein an amount of complement C3, complement factor B, complement MAC protein, complement C5b, complement C6, complement C7, complement C8, and / or complement C9 measured in (a) that is greater than the amount of complement C3, complement factor B, complement MAC protein, complement C5b, complement C6, complement C7, complement C8, and / or complement C9 measured in the control sample identifies the meningitis in the subject as bacterial meningitis.