Jeju Island health officials have launched an emergency pest-control operation following a sharp increase in mosquitoes that transmit Japanese encephalitis [1, 2].

The surge represents a public health risk because these insects carry a viral brain infection. The early arrival of the vector population forces local authorities to accelerate vaccination and prevention efforts to avoid seasonal outbreaks [1, 2].

Unseasonably early warm temperatures and humid, rainy weather have created ideal conditions for mosquito breeding [1, 2]. Daytime temperatures have risen to between 20 °C and 25 °C [1], a range that accelerates the spread and population growth of mosquitoes and midges [1].

Local data indicates a significant presence of the insects in urban areas. In downtown Jeju, an average of approximately 15 mosquitoes are being captured per day this month [1]. This volume has placed Jeju in second place nationwide for mosquito capture numbers, trailing only Jeollabuk-do [1].

Health-center pest-control staff are currently focusing their efforts on areas with high volumes of public complaints [1]. These teams are deploying insecticides in residential neighborhoods, specifically targeting areas around "clean houses," the island's waste collection points [1].

A Jeju health-center pest-control officer said, "As daytime temperatures rise to 20 to 25 degrees, mosquitoes and midges spread and their numbers increase, so we are taking intensive measures in areas where there are complaints" [1].

Reporter Kim Yong-won of KCTV Jeju said that pest control personnel are spraying insecticides around clean houses in residential areas [1].

“Jeju ranks second in mosquito capture numbers nationwide, after Jeollabuk-do.”

The early surge of Japanese encephalitis vectors on Jeju Island suggests a shift in seasonal patterns likely driven by abnormal spring warming. Because the island is a primary tourist destination in South Korea, an early peak in mosquito activity increases the risk of viral transmission to both residents and visitors before typical seasonal precautions are fully implemented.