Health experts at the University of Sydney are calling for greater awareness of the risks of encephalitis, after research found that more than half (58 percent) of children diagnosed with the condition do not make a full recovery within 12 months.

Encephalitis is an acute inflammation of the brain tissue most commonly triggered by an infection after a virus such as influenza, measles, or herpes. It can also be caused by infections transmitted by the bite from a mosquito or tick. 

Although a rare condition, it is more common than bacterial meningitis and can be life-threatening if not treated early. 

Associate Professor Philip Britton, from the University of Sydney Infectious Diseases Institute, said: “Encephalitis is a rare but serious condition and it's important parents are aware of the risks and how to mitigate them. 

“Encephalitis is often triggered by common viruses like influenza or measles, so one way parents can protect their children is to stay on top of regular and seasonal vaccinations. 

“Another important step is to know the symptoms, like fever with confusion, weakness, or problems with speech, and to take action quickly. Getting a child to hospital as soon as symptoms present is vital to ensure early diagnosis and treatment.” 

Symptoms of encephalitis 

Encephalitis usually begins with flu-like symptoms, such as a high fever or a headache, before developing into more serious symptoms including seizures, confusion, neck stiffness and extreme drowsiness. 

In the long-term effects can include fatigue, muscle weakness, changes in vision and hearing and trouble with speech. 

Research 

The researchers identified more than 700 children (aged 0-15 years) who were suspected of having encephalitis in five paediatric hospitals in Australia. Of these cases, more than 400 went on to be confirmed as encephalitis, with their outcomes monitored once at discharge and again 12 months afterwards.

The study found that the worst health outcomes at 12 months were associated with infectious encephalitis and among children who stayed longer in hospital or who had a longer stay in intensive care; whose behavioural or personality changes lasted for more than 24 hours; and whose symptoms included motor weakness. 

Meanwhile, some children with immune-mediated encephalitis, who developed the condition as a result of their body overreacting to an infection, generally showed the greatest improvement between discharge and the 12-month follow up period. 

Dr Britton said: “Childhood encephalitis is a serious condition, with many children experiencing long-lasting neurological problems. 

“It is important that children who get encephalitis are monitored closely for at least 12 months after diagnosis so that they can get support for recovery tailored to their needs.” 

Research: 

Britton, P.N., et al ‘Long-term outcomes of childhood encephalitis in Australia: burden and predictors from the Australian childhood encephalitis (ACE) prospective multicentre cohort (Lancet Regional Health – Western Pacific, 2026)

DOI: https://doi.org/10.1016/j.lanwpc.2026.101951

Declaration:

The research was conducted with funding from the National Health and Medical Research Council (NHMRC). Prof Dale was a member of a Data Safety and Monitoring Board for a Roche sponsored trial for paediatric multiple sclerosis. Prof Marshall is an investigator on clinical trials sponsored by Sanofi, Pfizer and Seqirus, but receives no personal payments from industry sponsors. Prof Marshall was a member of a Data Safety and Monitoring Board for a Glaxo-Smith-Kline sponsored trial and has received speaker travel support from GSK. All other authors have no competing interests to declare.