KATHMANDU, NOVEMBER 7

Japanese Encephalitis (JE), the most common laboratory-confirmed encephalitis in Nepal, is a viral disease causing inflammation of the brain. It is primarily spread through mosquito bites and is caused by the Japanese Encephalitis Virus (JEV), a flavivirus related to dengue, yellow fever, and West Nile viruses.

JEV is transmitted mainly by the female 'Culex tritaeniorhynchus' mosquito, which becomes infected after biting pigs or water birds, the primary carriers of the virus. The virus is then passed to humans when the infected mosquito bites them.

It is not transmitted from human to human. Infected humans do not carry enough viral load to infect mosquitoes, making them 'dead-end' hosts. The disease is most prevalent in regions where humans live in close proximity to the animal hosts, exacerbating the risk.

According to the World Health Organization (WHO), JEV primarily circulates between mosquitoes, pigs, and water birds. It is mainly transmitted during the warm season in temperate regions, with outbreaks intensifying during the rainy season in rice-cultivating areas.

Impact on Nepal

Despite efforts to curb its spread, Japanese encephalitis continues to be a seasonal threat in Nepal, particularly between April and October.

Recent data from the Early Warning and Reporting System (EWARS) highlights the persistence of the virus, with 139 reported cases in 2022 and 107 cases in 2023. However, experts believe the actual number of infections could be much higher, as the World Health Organization (WHO) estimates up to 300 unreported cases for every confirmed one.

While most Japanese Encephalitis infections are asymptomatic or present with mild symptoms like fever and headache, approximately 1 in 250 cases result in severe illness. The typical symptoms include high fever, headache, vomiting, unconsciousness, stiff neck, body convulsions, and abnormal limb movements. In the advanced stages, patients may develop a dull mask-like face, tremors, rigidity, and seizures.

It's fatality rate can reach up to 30%, and 30-69% of survivors may experience neuropsychiatric sequelae, including memory loss, speech difficulties, and muscle weakness. The condition often leaves lasting effects on children, with up to 50% suffering from permanent neurological damage, WHO says.

The Ministry of Health and Population (MoHP) urges everyone to prevent mosquito bites by keeping animals such as pigeons, chickens, and pigs in secure enclosures, wearing long-sleeved clothing outdoors, installing nets on windows and doors, and draining stagnant water around the house.

According to the Family Welfare Division (FWD), 61 positive cases from 695 samples tested nationwide this year, with most cases affecting children under 15, according to the FWD data up to September 2024. So far, 14 fatalities (22.95%) have been recorded, with deaths reported from Kailali, Kapilvastu, Palpa, Chitwan, Sindhuli, Rautahat, Sarlahi, Siraha, Sunsari, and Jhapa, the data said.

Prevention and Vaccination

While there is no specific antiviral treatment for JE, vaccination remains the most effective method of prevention. The JE vaccine has been incorporated into Nepal's national immunization schedule since 2009, with children receiving it at 12 months of age. Since the launch of the vaccination program, significant progress has been made, with a notable decline in cases. However, sporadic outbreaks continue, often due to lapses in immunization campaigns.

WHO recommends continued vaccination efforts, alongside surveillance and reporting, in areas where JE is a public health priority. It is estimated that 12 million people are at risk of JE in Nepal.

Japanese Encephalitis in Nepal

The first case of Japanese encephalitis viral disease (JE) was documented in 1871 in Japan. Since the first case of JE was detected in Rupandehi in 1978, Nepal has been actively monitoring the disease. The country witnessed national vaccination campaigns in 2004, 2006, 2011, and 2016. Research indicates that three strains of JEV, namely Nep-1/90, B-2524, and B-9548, have been isolated in Nepal.

Globally, JE causes an estimated 13,600 to 20,400 deaths annually. In 2005, a devastating outbreak in India and Nepal claimed nearly 2,000 lives, most of them children, according to WHO. However, awareness of the disease remains low, and the true impact of JE, particularly its long-term neurological consequences, is often underestimated, it added.

While JE is a preventable disease, its high fatality rate and severe long-term effects on survivors make it a major public health concern. Public health experts urge continued vaccination efforts and heightened awareness to control its spread and minimizing its impact, especially in vulnerable rural areas.