Fifty-seven per cent of childhood encephalitis cases were caused by infections,according to the study. The majority were common viruses and bacteria such as enterovirus (10 per cent),parechovirus (10 per cent),as well as vaccine-preventable influenza (6 per cent) and herpes simplex virus (6 per cent).
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One quarter of the children had “immune-mediated” encephalitis.
“What we think is happening is these children get an infection and their bodies get tricked into thinking the brain is foreign so they have an auto-immune reaction,” Dr Britton said.
For another 17 per cent of children,the cause of their encephalitis is unknown.
“Many,many children will be infected in the community but only one in 1000 infected children will get severe disease,” Dr Britton said. “That ratio holds true for most of the leading causes of encephalitis.
It was not known why only a small number develop life-threatening encephalitis.
“We just don’t have the answer to that,” Dr Britton said.
Though future genomic and molecular research may determine whether certain children have genetic vulnerabilities that make them more susceptible,or whether specific infections mutate into more virulent forms,he said.
Influenza one of the common causes of encephalitis and responsible for two of the 14 deaths,but four in five children eligible for the flu vaccine were not immunised.
“Vaccination is our most powerful preventative tool for infectious diseases,” Dr Britton said. “We need to be heading upwards for 80 per cent for flu vaccine coverage in children.”
The study found infectious encephalitis was more common in younger children. Infants under three months old were particularly vulnerable,Dr Britton said.
“We don’t want to alarm parents but we need families to practice good infection control:washing hands and keeping older snotty and unwell siblings away from littler babies is important,” he said.
Dr Gabrielle Haeusler infectious disease physician at the Murdoch Children’s Research Institute said the “exceptionally important” study highlighted the potentially devastating effects of what many perceive as common and harmless childhood illness.
“While not all children that get these viruses go on to have these severe neurological effects we have no way to predict which kids will and won’t therefore prevention is vital,” Dr Haeusler said.