Encephalitis is a Vaccine-Preventable Global Threat

The World Health Organization (WHO) recently published a technical brief on encephalitis, a serious, life-threatening neurological condition characterized by brain inflammation.

On February 17, 2025, the WHO stated that different pathogens, such as herpes simplex virus (HSV), can cause encephalitis. 

Some pathogens, like the Japanese encephalitis virus (JEV), are spread by mosquitoes and ticks, but vaccination can prevent transmission.

As of 2025, JEV outbreaks are the leading cause of viral encephalitis in twenty-four countries in the WHO South-East Asia and Western Pacific Regions, exposing more than 3 billion people to infection risks.

For example, the WHO reported various JEV cases across Australia, including Queensland, New South Wales, South Australia, Victoria, the Australian Capital Territory, Tasmania, Western Australia, and the Northern Territory.

Encephalitis affects people across all age groups, has high mortality, and often leads to significant long-term complications (sequelae), including hearing loss, seizures, limb weakness, and difficulties with vision, speech, language, memory, and communication.

Globally, in 2021, encephalitis was the fourth leading cause of neurological health loss in children aged under 5 years and the 13th across all age groups.

"Encephalitis is a growing public health challenge, and by prioritizing it within global and national health agendas and strengthening collaboration, we can reduce its impact and save lives," said Dr Tarun Dua, Head of the Brain Health Unit, WHO, in a press statement.

The WHO technical brief, which forms part of the implementation of the broader Intersectoral global action plan on epilepsy and other neurological disorders, draws attention to the lack of access to essential care, especially in low-and middle-income countries. 

While no HSV vaccines are authorized, the U.S. FDA-approved JEV vaccine, IXIARO®, is available at clinics and pharmacies nationwide. According to the U.S. CDC, vaccination is recommended before visiting JEV outbreaks.