Rats, long unseen in Seoul, emerge from the shadows

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For years, the rats of Seoul were a footnote, an unseen part of the urban landscape.

This summer, however, they’ve come out of the shadows, forcing the capital to confront a rodent problem that has residents on edge and officials scrambling for a response.

Flooding and relentless summer rains have brought the rats out of hiding, leading to a surge in sightings across streets and transit hubs.

The number of complaints filed on local government bulletin boards over rat sightings has increased recently, according to Gangnam and Gangdong district offices.

Climate change has been cited as one of a key driver of the sightings.

Warmer temperatures are allowing more rats to survive through winter, while also extending their breeding season. Once limited by the harsh cold, the rodents are now skipping or shortening their hibernation periods, reproducing continuously throughout the year and driving their population to rise at a faster pace.

The nationwide average temperature last fall climbed to 16.8 degrees Celsius, exceeding the seasonal average by 2.7 degrees.

Torrential rains are also pushing rats above ground, as flooded sewers wipe out their habitats and drive them into city streets and neighborhoods, where they are increasingly visible to residents.

Another major factor behind the growing problem is aging infrastructure. A significant portion of Seoul's drainage and sewage pipes — over 3,300 kilometers, or 30 percent, of the network — is more than 50 years old. An additional 55 percent of the pipes are over three decades old.

These older, more fragile pipes are easily compromised by rodents, allowing rats to chew their way in and create large colonies that can spread quickly throughout the city, according to experts.

Similar trends are being observed worldwide.

A study in the journal Science Advances found that rat populations have increased in 13 out of 16 surveyed cities across countries including the United States, Japan and elsewhere. In Washington D.C., the number of rats has quadrupled over the past decade.

Because Korea does not separately track rat sightings, it was excluded from the study. However, the study found that rat populations tend to grow faster in densely populated cities with limited green space.

Concerns are also mounting over diseases transmitted by rats.

One example is hemorrhagic fever with renal syndrome, transmitted through rat urine or secretions. Symptoms include high fever, hemorrhaging and kidney failure, with a fatality rate of up to 15 percent. Another is leptospirosis, which can cause fever and muscle pain and become life-threatening in severe cases. The disease has no vaccine, making prevention all the more important.

In addition, rat-related complaints have increased, prompting district offices across Seoul to step up pest control efforts. In Gangnam District for example, smart traps are being installed, while Gangdong District has already rolled out 80 of the devices.

The Seoul Metropolitan Government has urged residents to immediately report sightings to their district office or local public health center.

“When a complaint about a rat sighting is received, we immediately begin pest control,” a Seoul city official said.