Viruses most common cause of meningitis: Study

Viruses are now the most common cause of meningitis in adults and a cause of substantial long-term ill health, a major UK study has found.

Researchers at the University of Liverpool in the UK studied the diagnosis and treatment of more than 1000 patients with suspected meningitis.

They found that diagnosis of meningitis is often delayed due to unnecessary brain scans being performed before lumbar puncture - which is the essential investigation to determine the cause of the illness.

The majority of patients (81 per cent) had a brain scan and 70 per cent of those took place before lumbar puncture, otherwise known as a spinal tap.

Recommendations urge doctors to perform a lumbar puncture within the first hour in patients with suspected meningitis unless the patient has particular symptoms which make it unsafe.

Only 12 per cent of patients studied should have had a brain scan prior to lumbar puncture if the guidelines had been followed.

Cases of bacterial meningitis - the life-threatening form of the disease - have significantly reduced over the last few decades following the introduction of vaccines against some of the most common types, and the study found that viral meningitis now accounts for the majority of cases.

Being able to quickly determine which bacteria or virus is causing the illness is essential for the appropriate treatment of patients. Antibiotics should be given urgently to those with bacterial meningitis, but not viral meningitis, as viruses don't respond to antibiotics.

Delays in diagnosis mean that antibiotics are often inappropriately used in patients with viral meningitis, resulting in a longer than necessary stay in the hospital, and potentially also contributes to the problem of antimicrobial resistance.

For the study published in The Lancet Infectious Diseases journal, patients in the new study who were investigated promptly with lumbar puncture were also more likely to have a specific cause of meningitis identified and to spend less time in the hospital.

Overall, the specific virus or bacteria causing the illness was not identified for 43 per cent of patients.

"This study provides the first estimate of the incidence of viral meningitis in UK adults. It shows that viral meningitis is now a major cause of meningitis, but often the management is not quite right," said Fiona McGill from the University of Liverpool.

"It's a concerning finding that so many unnecessary brain scans are taking place and that these appear to be delaying the correct diagnosis," said McGill.

"Diagnosing a specific cause of meningitis quickly is key to getting patients on the right antibiotics if needed, or avoiding unnecessary antibiotics in those with viral meningitis," said Mike Griffiths, senior investigator on the study.