Incidence, aetiology, and sequelae of viral meningitis in UK adults: a multicentre prospective observational cohort study

Abstract

Background: Viral meningitis is increasingly recognised, but little is known about the frequency with which it occurs, or the causes and outcomes in the UK. We aimed to determine the incidence, causes, and sequelae in UK adults to improve the management of patients and assist in health service planning.

Methods: We did a multicentre prospective observational cohort study of adults with suspected meningitis at 42 hospitals across England. Nested within this study, in the National Health Service (NHS) northwest region (now part of NHS England North), was an epidemiological study. Patients were eligible if they were aged 16 years or older, had clinically suspected meningitis, and either underwent a lumbar puncture or, if lumbar puncture was contraindicated, had clinically suspected meningitis and an appropriate pathogen identified either in blood culture or on blood PCR. Individuals with ventricular devices were excluded. We calculated the incidence of viral meningitis using data from patients from the northwest region only and used these data to estimate the population-standardised number of cases in the UK. Patients self-reported quality-of-life and neuropsychological outcomes, using the EuroQol EQ-5D-3L, the 36-Item Short Form Health Survey (SF-36), and the Aldenkamp and Baker neuropsychological assessment schedule, for 1 year after admission.

Findings: 1126 patients were enrolled between Sept 30, 2011, and Sept 30, 2014. 638 (57%) patients had meningitis: 231 (36%) cases were viral, 99 (16%) were bacterial, and 267 (42%) had an unknown cause. 41 (6%) cases had other causes. The estimated annual incidence of viral meningitis was 2·73 per 100 000 and that of bacterial meningitis was 1·24 per 100 000. The median length of hospital stay for patients with viral meningitis was 4 days (IQR 3-7), increasing to 9 days (6-12) in those treated with antivirals. Earlier lumbar puncture resulted in more patients having a specific cause identified than did those who had a delayed lumbar puncture. Compared with the age-matched UK population, patients with viral meningitis had a mean loss of 0·2 quality-adjusted life-years (SD 0·04) in that first year.

Interpretation: Viruses are the most commonly identified cause of meningitis in UK adults, and lead to substantial long-term morbidity. Delays in getting a lumbar puncture and unnecessary treatment with antivirals were associated with longer hospital stays. Rapid diagnostics and rationalising treatments might reduce the burden of meningitis on health services.

Funding: Meningitis Research Foundation and UK National Institute for Health Research.

Figure 1

Flow chart of study and final diagnoses of patients recruited CSF=cerebrospinal fluid. *Patients were screened on receipt of a CSF sample in the laboratory. The majority of patients screened and subsequently not recruited did not have meningitis in the differential diagnosis. Mostly, patients had a lumbar puncture to rule out subarachnoid haemorrhage. †Of the non-meningitis cases, 123 were non-specified viral illnesses, 18 were urinary tract infections, 94 were other infections, 95 were headaches or migraines, and 124 were other or unknown illnesses. ‡Median CSF leucocyte count was 12·5 × 10⁶ cells per L (IQR 6–46), and 22 of 41 patients had a leucocyte count of <10 × 10⁶ cells per L. §See table 2 for more details.

Figure 2

Number of patients with a proven microbiological diagnosis following delay in lumbar puncture Lines represent the percentage of all patients with a pathogen detected. Bars represent actual numbers of patients. Data beyond 28 h are not shown because of small numbers.

Figure 3

EQ-5D-3L scores over time from acute illness for meningitis The EQ-5D-3L determines health status across five domains, which is converted into a utility score. A score of 1 represents best health and 0 represents dead. Health states perceived to be worse than death have a negative score. Datapoints are mean scores, and error bars indicate SDs. Median age for viral meningitis was 32 years (IQR 24–42), and median age for bacterial meningitis was 56 years (34–65).