What is encephalitis? A new study breaks down the numbers

Encephalitis, which means inflammation of the brain, is a severe disease. Sometimes the inflammation can involve the lining of the brain (the meninges) as well, and is referred to as meningo-encephalitis.

Adults and children who develop encephalitis need to be cared for in hospital and many are admitted to the intensive care with seizures or varying levels of coma. The disease can be fatal.

How many cases of encephalitis in children?

Encephalitis can be caused by infections but also the body’s own immune system in a process called auto (or self)-immune disease.

In a major University of Sydney-led study in the prestigious journal Clinical Infectious Diseases published this week, we have described the causes and consequences of encephalitis in Australian children from 2013-2016.

Almost 300 children with encephalitis were identified in major Australian Children’s Hospitals around part of the Paediatric Active Enhanced Disease Surveillance (PAEDS) network,)) funded by the Commonwealth Department of Health and state Departments of Health.

An accompanying editorial in the same journal states: “the impressive study by Britton et al… shows just how far we have come in the last decade in terms of improving the diagnosis of encephalitis aetiologies and just how far we must go in terms of improving outcomes of this often-devastating disease”.

Among the children identified, one in four suffered moderate to severe brain injury, underlining just how severe the condition can be, and one in 20 died from the disease. Encephalitis needs greater recognition as a cause of childhood death and disability among Australian children.

The disease affected children of all ages but infections predominantly affected the youngest children, aged under five years; auto-immune diseases tended to affect older children.

What causes encephalitis?

Some of the leading infections causing encephalitis were:

• Enteroviruses (that most often cause hand, foot and mouth disease) and a closely related virus called parechovirus, both of which occurred in outbreaks mainly in the spring/summer/autumn period
• Influenza – as expected these cases occurred during the annual influenza season. There is a need to boost the uptake of seasonal influenza vaccination amongst children to help prevent these cases into the future.

These infections are typically passed to young children by older siblings or parents and may also be passed around childcares and preschools.

An encouraging finding was the absence of the chicken-pox virus (varicella-zoster virus; VZV) as a cause almost certainly because Australia’s national immunisation program has funded VZV vaccine since 2007 and achieved high vaccine use across the country.

The outbreaks of enterovirus and parechovirus were caused by new viruses to Australia – so-called emerging infections – which underscores the importance of ongoing surveillance and preparation on behalf of the Australian health system.

Pleasingly, the Commonwealth department of health has committed to ongoing encephalitis surveillance which will ensure Australia’s readiness to detect and respond in the future.

The most common cause also the most mysterious

But, we face ongoing challenges. Many (one in five) of the children identified by the study did not have a cause diagnosed for their illness. This is a major gap and we will continue to work to ensure all children in Australia receive optimal testing, but we also need access to cutting edge research tools to enhance our efforts.

Further, the most frequent cause identified – acute disseminated encephalomyelitis (ADEM)  is a mysterious auto-immune condition that is poorly understood but seems to be increasingly common.  Why do children get ADEM and what is the best way to treat it? More research is required.

Overall, as the editorial emphasises, encephalitis is a neglected, severe disease with limited high-level clinical trial evidence to guide its management and so improve outcomes.

“The time has come to move beyond causality and toward the global goal of optimising management for this devastating syndrome,” the editorial reads.