Not all cases of encephalitis show an increase in blood counts. Elevated blood counts in encephalitis generally occur in bacterial infections, such as the most common pyogenic meningitis. This can cause a significant increase in blood counts, predominantly with neutrophils. Tuberculous meningitis can also show elevated blood counts, but not as prominently as pyogenic meningitis. In cases of viral infection, such as the common herpes simplex virus infection, patients might experience a decrease in blood counts. This is characterized by a reduction in the total number of white blood cells, a lower proportion of neutrophils, and a possible increase in lymphocyte proportion. If the patient has a concurrent lung infection or other bacterial infections at different sites, there might be an increase in blood counts, which can mask the blood abnormalities originally caused by the viral infection.