Malaria-carrying mosquitoes detected in Seoul two weeks earlier than usual

The Seoul Institute of Public Health and Environment announced Wednesday that its mosquito surveillance program has detected disease-vector mosquitoes appearing earlier than in previous years.

Overall mosquito activity this year is on par with historical averages, but malaria-carrying mosquitoes were collected two weeks ahead of schedule, while mosquitoes capable of transmitting dengue and other imported infectious diseases were collected one week early. Analysis of vector mosquitoes collected across Seoul to date has found no infectious disease pathogens.

With Japanese encephalitis alerts and malaria advisories now in effect nationwide, Seoul authorities are urging heightened vigilance as disease-vector mosquitoes continue to appear across the city. The Korea Disease Control and Prevention Agency (KDCA) issued a nationwide Japanese encephalitis alert on June 17 after the Japanese encephalitis virus gene was detected in a vector mosquito — the small brown house mosquito — collected in Daegu. That alert came more than a month earlier than in previous years. A nationwide malaria advisory followed on June 22, triggered when three or more cities, counties or districts recorded a daily average mosquito index of 0.5 or higher. The areas that met the threshold were Guro-gu in Seoul, Paju in Gyeonggi Province, Ganghwa-gun in Incheon and Yanggu-gun in Gangwon Province.

Authorities noted that in 2024, when vector mosquitoes also appeared early as they have this year, mosquito-borne infections in Seoul subsequently increased — underscoring the need for sustained surveillance and active control measures. The institute said it will continue monitoring vector mosquitoes and testing for pathogens, and will immediately share any anomalous findings with relevant agencies to enable a rapid response.

Residents are advised to eliminate standing water near their homes, wear long sleeves and long pants during outdoor activities, and use insect repellent. Anyone who develops suspicious symptoms should visit a medical facility promptly.

Because mosquitoes can breed in even small amounts of standing water, residents should regularly empty water from flowerpots and containers, participate in larval control efforts for septic tanks and drainage sumps, and check that window and door screens are intact.

Anyone who develops chills, high fever or other suspicious symptoms after visiting a malaria-risk area should go immediately to a public health center or medical facility. Military personnel discharged within the past two years after serving in a risk area may receive free testing at a nearby public health center even if they have no symptoms.

Park Ju-seong, director of the Seoul Institute of Public Health and Environment, said the institute would closely monitor mosquito activity and trends in vector-borne disease to stay ahead of potential outbreaks. "We also ask residents to tidy up their surroundings, check their window screens, and practice personal protective measures such as wearing long sleeves and using repellent when outdoors to avoid mosquito bites," Park said.

The institute has been conducting mosquito surveillance across Seoul since March 30, and the results are available on its website and through the Seoul Open Data Plaza.