Encephalitis “remains under-recognized, under-diagnosed, and underfunded”,  according to a new policy report from the World Health Organization (WHO).

Climate change, vaccine hesitancy, and the rising burden of vector-borne diseases are also fuelling an increased number of encephalitis cases, a rare but serious inflammation of the brain. 

The technical document urges coordinated global action to “confront and tackle the growing public health threat from encephalitis,” and points to prevention strategies, as well as gaps in diagnosis, research, treatment, and care. 

“Unless prompt action is taken, encephalitis will continue to drive avoidable deaths and disability,” notes Encephalitis International, a global advocacy non-profit.

“Regrettably, the withdrawal of support for the WHO and potential dissolution of USAID by President Donald J Trump’s Administration, among other recent executive actions, threaten to worsen an already challenging situation,” said the non-profit in a statement.

The report comes as measles, which in some cases can cause encephalitis ,continues to plague higher-income countries, including a recent outbreak in West Texas, where a “close-knit, undervaccinated” Mennonite community is at the epicentre of a 58-person outbreak.

Vaccine skeptics received a strong boost in the confirmation of Robert F Kennedy Jr as Secretary of the Department of Health and Human Services. The Secretary spent more than 30 years sowing doubt as to the safety of vaccines. Measles, mumps, and rubella–diseases prevented by routine childhood vaccines–can also in some cases cause encephalitis. 

‘Life-threatening’ brain inflammation

Encephalitis, the swelling of the brain, affects people across all age groups, and has high mortality rates. 

“Unlike other organs or organ systems, the brain is very sensitive to swelling and inflammation…when the brain is injured, it can have permanent effects on the brain’s function – like walking, talking, even causing seizures,” said Dr Youssef Kousa, a neurologist and founder of the Zika Genetics Consortium at Children’s National Hospital, in an interview with Health Policy Watch.

“For a lot of encephalitdes, there are no treatments.”

The condition often leads to significant long-term complications including hearing loss, seizures, limb weakness, and difficulties with vision, speech, language, memory and communication, according to the WHO.

Globally in 2021, encephalitis was the fourth leading cause of neurological health loss in children under five years and the 13th across all age groups. The report notes that in the same year, over 80,000 people died from encephalitis and up to 50% of people with encephalitis suffered long-term after-effects of the condition, losing “independence, income and quality of life.”

Underdiagnosed and lacking political commitment

“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 at the WHO, in a press release. 

“These efforts will not only improve health outcomes and quality of life for those affected and their families but also result in stronger, more resilient health systems.” The Brain Health Unit at WHO was only formed in 2020, as a growing number of brain-related conditions affect both lower and higher income countries, notably Alzheimer’s, Parkinson’s, epilepsy, and encephalitis. 

“I sit here just as Oropouche virus is increasing in cases in South America, right now and as yet, barely studied. Without surveillance, this virus will continue to spread almost unnoticed,” said Dr Aline MB Matos, a neurologist from São Paulo, Brazil, at the report’s launch on Wednesday.

“Encephalitis today is not a funding priority in many low and middle income countries, not because it is not important, but because these countries face multiple crises. Lack of clean water, limited access to education, an overburdened healthcare system, armed conflicts. And as a reality, it is difficult to choose what to prioritize.

“But encephalitis must be a priority.”

Diagnosis in lower-and-middle income countries is especially difficult, because the condition requires a confirmatory lumbar puncture, and sometimes highly specialized tests such as brain imaging and electroencephalography (EEG). However, as the report notes, and as Matos highlighted in her remarks, most of the world’s population lives in areas with no immediate access to comprehensive or rapid encephalitis diagnostics. 

“In many countries, lumbar punctures are performed on only some of the people with suspected brain infections. This may be due to a lack of trained workforce or procedural kits, and misconceptions about lumbar puncture indications and safety,” noted the report. 

But even in higher-income countries, there are only so many treatments for the viruses that cause encephalitis, said Kousa. Even if Zika or West Nile Virus can be diagnosed more readily in the US, providers have nearly the same limited treatment options as those in lower-income countries. 

Vector-borne diseases pose new threat 

Several pathogens can cause encephalitis, with the herpes simplex virus being the most common cause of the condition, according to the WHO. But other viruses, notably vector-borne diseases, are a rising threat for encephalitis. 

Dengue, Zika virus, and oropouche virus are all increasing in incidence and prevalence in South America, the Caribbean, and South and South-East Asia, as warming climates, deforestation, and urbanization spur mosquitoes into closer proximity to humans. Almost half of the global population is now at risk for these diseases.

Recent dengue outbreaks have plagued the Indian subcontinent, and oropouche virus, a relatively rare vector-borne disease, is likely to see case levels similar to last year’s record-breaking season.

Also of concern is Japanese Encephalitis virus (JEV), which has now spread to 24 South-East Asia and Western Pacific countries, including Australia, and a novel tick-borne encephalitis. 

“We do not know the full number of encephalitis cases worldwide, but we do know that infectious causes play a major role, and in low and middle income countries, many of these pathogens are either emerging or being neglected,” said Matos. The problem is only exacerbated by climate change, as previously uninhabitable regions become mosquito breeding grounds. 

“This renders large populations at increasing risk of vector-borne diseases such as arboviruses,” noted the report.

While these diseases have few – or even no – vaccines, some more established, and vaccine-preventable diseases, are seeing a resurgence.

Encephalitis-inducing viruses can be prevented by vaccines, such as influenza, varicella-zoster virus (VZV), rabies, poliomyelitis, and measles, mumps and rubella (MMR). The COVID-19 pandemic-related disruptions in routine immunizations and vaccine hesitancy have left experts worried about encephalitis cases due to MMR. 

“Vaccine hesitancy is an issue for us, and it’s part of this bigger picture science skepticism and false information. So it’s up to us as a community to push out the right messages,” said Dr Tom Solomon CBE, a neurologist at Liverpool University Brain Infections Group, at the report launch. Solomon is also President of Encephalitis International and an advisor to the WHO

Hopes that WHO support will lend greater awareness

For Professor Benedict Michael, a neurologist at the University of Liverpool, the new report “puts encephalitis on the map,” building on the advocacy successes in the past decade. While epilepsy and Parkinson’s have garnered more attention on the brain health front, the experts gathered at the Encephalitis International-WHO launch hope that the report will improve public health policies, including vaccine programs and vector control. 

“Encephalitis is just one example of why working together matters. From COVID-19 we learnt diseases do not respect borders, politics or ideologies. They affect us all,” said Dr Aline MB Matos.

Understanding the disease burden through improved surveillance, and improving patient care in rehabilitation and access to healthcare were also high on the priority list.

“Our recent research has shown that many of the interventions needed to improve diagnosis and treatment of encephalitis are not particularly expensive. A lot of it is about increasing surveillance and recognition of the condition, providing simple equipment for early diagnosis, and making sure the right treatments, many of which are very affordable, are available,” said Solomon.

The report points to several key factors that would reduce the burden of encephalitis, stating countries should prioritize relevant medicines for inclusion into national essential medications lists and standardized treatment protocols, include both autoimmune and infectious encephalitis and their treatments in publicly funded UHC packages, use and expand existing surveillance systems for forecasting demand and supply chains, and pair better availability and affordability of medicines with appropriate training and education of the health workforce to recognize and treat encephalitis in a timely manner. 

“There’s huge potential for this technical brief to have genuine global impact that’s transformative in the brain health agenda,” concluded Benedict.

Image Credits: Flickr: Florey Institute of Neuroscience & Mental Health, WHO, WHO, Encephalitis International.