Viral meningitis

Viral meningitis is common and often goes unreported. In the absence of a lumbar puncture, viral and bacterial meningitis cannot be differentiated with certainty, and all suspected cases should therefore be referred. Lumbar puncture and analysis of cerebrospinal fluid may be done primarily to exclude bacterial meningitis, but identification of the specific viral cause is itself beneficial. Viral diagnosis informs prognosis, enhances care of the patient, reduces the use of antibiotics, decreases length of stay in hospital, and can help to prevent further spread of infection. Over the past 20 years, vaccination policies, the HIV epidemic, altered sexual behaviour, and increasing travel have altered the spectrum of causative agents. In this review we outline the changing epidemiology, discuss key clinical topics, and illustrate how identification of the specific viral cause is beneficial. Neonatal meningitis may be a component of perinatal infection and is not covered here. #### Summary points #### Definitions