Health authorities advise Japanese encephalitis vaccinations after year's first cases confirmed

National health authorities on Tuesday advised people to get vaccinated to prevent infections of mosquito-borne Japanese encephalitis virus (JEV) after they confirmed the year's first two human cases.

A Culex tritaeniorhynchus mosquito [KOREA DISEASE CONTROL AND PREVENTION AGENCY]

National health authorities on Tuesday advised people to get vaccinated to prevent infections of mosquito-borne Japanese encephalitis virus (JEV) after they confirmed the year's first two human cases.

The Korea Disease Control and Prevention Agency (KDCA) said the two patients in their 60s were diagnosed with the infection last Thursday after displaying a four-fold rise in antibodies between the initial testing and a second round of testing two or three weeks later. The agency said the four-fold increase is the threshold for judging an infection.

The agency said that the two patients are currently hospitalized and receiving treatment. They suffer from high fever, vomiting, dizziness and a decline in cognitive function.

An epidemiological survey found that both had recently participated in outdoor activities such as weed removal and plowing. The health agency also confirmed the two patients were unvaccinated and had mosquito bites.

Before the two latest infections, the agency issued a nationwide advisory and warning for JEV in March and July, respectively.

In Korea, most JEV cases occur between August and November, with around 80 percent of confirmed cases reported in September and October.

By age group, people aged over 50 accounted for 87.9 percent of all yearly registered cases, an official from the KDCA told the Korea JoongAng Daily.

Most JEV cases resulted in light symptoms such as fever and headaches. However, in some occasions, it can develop into encephalitis, with severe symptoms such as high fever, seizure, cramps and paralysis and a fatality rate of around 20 to 30 percent.

Once the virus develops into encephalitis, 30 to 50 percent of the patients can experience neurological complications, depending on which parts of the brain are affected by the virus. Such attributes make swift diagnosis and treatment more crucial, the KDCA said.

The KDCA asked people born after 2011 to receive immunization shots for free as “effective vaccines are available under the national standard immunization schedule.”

It also recommended unvaccinated people over 18 who live near farms or pigpens or who plan to travel to high-risk areas to pay for immunization shots. The agency asked foreigners from non-endemic regions to get vaccinated if they will stay in Korea for a while.

The U.S. Centers for Disease Control and Prevention designated 25 countries as areas at risk for Japanese encephalitis, including Korea, Japan, China, Thailand, India and Australia.

JEV is mostly spread by dark-brown Culex tritaeniorhynchus mosquitoes, which live in rice fields, animal barns and puddles. They are nocturnal and active nationwide until the end of October.

The KDCA also added that it caught 322 Culex tritaeniorhynchus mosquitoes in the last week of August, more than the 271 mosquitoes it caught during the same period last year.

“Those subject to the immunization scheme should receive shots per the schedule, and individuals should follow prevention measures to avoid getting bitten by mosquitoes,” said Jee Young-mee, head of the KDCA. Jee also noted a “recent increase in mosquitoes” that can carry JEV.

BY LEE SOO-JUNG [lee.soojung1@joongang.co.kr]