Korea’s health authorities issued a nationwide warning against Japanese encephalitis Tuesday, and urged people to take precautionary measures including vaccination.

The Korea Centers for Disease Control and Prevention issued the warning in response to the rampant spread of the culex tritaeniorhynchus, a species of mosquito that carries the virus, in the Busan area.

In order to predict and act to prevent an epidemic, the KCDC has been collecting samples of mosquitos in 38 cities and provinces across the country. If the percentage of the carrier mosquito in a certain area exceeds 50 percent ― as in the case of Busan, with 53.3 percent ― a nationwide warning is issued.

The percentage of the cited species in the 37 other areas have yet to reach 50 percent, officials said.

The KCDC had issued a preliminary warning on the disease in April 21, when the mosquito was first spotted in the country.

Japanese encephalitis is transmitted by mosquito bites.

Most people who get bitten by mosquitoes carrying the disease do not experience any symptoms. But those who are infected can suffer from an array of symptoms ranging from fever, headache and nausea to seizures, paralysis, coma and even death.

Authorities have advised people to use window screens inside homes at all times until late October, and to wear long sleeves and pants during outdoor activities.

They also urged the public to get inoculated, especially children and the elderly, who have relatively weak immune systems.

By Yoon Min-sik (minsikyoon@heraldcorp.com)