Seven-fold increase in viral meningo-encephalitis reports in England and Wales during 2004–2013

In highly immunised populations viruses contribute to a substantially higher proportion of meningo-encephalitis cases. This national study aimed to describe population trends in laboratory-confirmed, viral meningo-encephalitis reports in England and Wales over a ten-year period. Laboratory-confirmed, viral meningo-encephalitis cases submitted by National Health Service hospitals in England and Wales during 2004–13 were analysed. There were 9941 laboratory-confirmed reports of viral meningo-encephalitis in England and Wales over the 10-year period. Number of reports increased across all age-groups and for all viruses from 311 (incidence, 0.6/100,000) in 2004 to 2168 in 2013 (incidence, 3.9/100,000). Median age at diagnosis was 30.6 (IQR, 1.3–51.5) years, with a third of cases diagnosed in children. In 2013, infants aged <3 months accounted for 27% (588/2168) of cases, but had the highest incidence (329/100,000). Enteroviruses were responsible for 52% (5133/9941) of all cases and 92% (1952/2121) in <3 month-olds (incidence, 313/100,000 in 2013, equivalent to 77/100,000 live-births) followed by herpes simplex (2885/9941; 29%) and varicella zoster (1342/9941; 13%), mainly among ≥45 year-olds. Increasing use of molecular testing has led to a 7-fold increase in laboratory-confirmed, viral meningo-encephalitis reports. Large clinical-observational studies are necessary to determine the burden of viral meningo-encephalitis, especially in infants.