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Encephalitis is a worldwide public health issue, with a substantially high burden among children in Southeast Asia. A large study of the causes of childhood encephalitis in SE Asia suggests that enhanced and effective vaccination against the Japanese encephalitis virus alone could reduce encephalitis prevalence by one third.

Group photo of the SEAe KOM ceremony

Published in Lancet Global Health, the study was conducted by the South-East Asia encephalitis (SEAe) project, a global collaboration coordinated by the Institut Pasteur (Paris), with partners in hospitals in the Lao PDR, Cambodia, Viet Nam and Myanmar and diverse reference laboratories.

The Lao site was coordinated by the MORU Tropical Health Network’s Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit (LOMWRU), embedded within the Microbiology Laboratory of Mahosot Hospital in Vientiane. A harmonised diagnostic system was used at Mahosot Hospital and elsewhere that allowed diagnosis of 23 treatable and key pathogens within 24 hours of patient admission.

"The high morbidity and mortality in conjunction with the high proportion of vaccine-preventable infections emphasises the enormous importance of enhanced vaccine coverage across Asia, of accessible evidence-based lab diagnostic strategies given the inaccuracies of clinical aetiological diagnosis, and appropriate and urgent empirical treatment, said Dr Sayaphet Rattanavong, research physician for the project in LOMWRU".

Encephalitis is inflammation that can result from a brain parenchyma infection, the functional tissue of the brain, or as a result of autoimmune response. It is a worldwide public health concern because of its high mortality rate and the neurological sequelae it causes. However, its causes often remain unknown. Viruses are the most frequent in case of infection but other pathogens may be responsible.  importantly, the study demonstrated the importance of prevention as well as rapid and appropriate diagnosis and treatment of patients suffering from encephalitis.

Of 694 children included in the SEAe study, 664 had encephalitis. A cause was identified in 64% of cases. The most common cause was Japanese encephalitis virus infection (33% of patients). The scientists also identified cases associated with dengue virus infection, influenza, herpes simplex virus 1, Mycobacterium tuberculosis, pneumococcus, enterovirus 71, other infectious agents (with more than 30 pathogens identified), and autoimmunity. Of all the causes identified, 18% were treatable and 42% could have been prevented by vaccination.

By the end of their hospital stay, 13% of the children had died, 23% had severe neurological sequelae, 30% had slight or moderate neurological sequelae, and 34% no sequelae. The risk factors for death or severe neurologic sequelae were related to meningeal tuberculosis, the presence of respiratory failure with oxygen requirements, the presence of prolonged coma, and delayed care.

"The data generated by this study will help in the development of diagnostic and preventive management recommendations for encephalitis in the Greater Mekong Region. They underline the importance of national mass vaccination campaigns targeting the Japanese encephalitis virus," said Marc Lecuit, (Université Paris Cité and Hôpital Necker-Enfants malades AP-HP), head of the Infection Biology Unit at the Institut Pasteur (Université Paris Cité, Inserm) and co-coordinator of the study.

Read the publication 'Childhood encephalitis in the Greater Mekong region (the SouthEast Asia Encephalitis Project): a multicentre prospective study' on The Lancet website.

About the South East Asia encephalitis (SEAe) Consortium 

The South East Asia Encephalitis (SEAe) Consortium brings together physicians and researchers from Europe and countries affected by childhood encephalitis in South-East Asia. It brings together a number of complementary partners with the aim of addressing some of the most important issues currently raised by encephalitis (including meningoencephalitis) in South-East Asia.