Tokyo's park mosquitoes spread dengue in 2014. Today the risk is minimal.

Yes, from roughly June to September, and you'll meet them by day in the places visitors seek out: parks, shrine forests, temple grounds and gardens. The biter is the Asian tiger mosquito, and the disease risk is minimal. Japan has no malaria, dengue isn't endemic, and the CDC doesn't recommend the Japanese encephalitis vaccine for a city stay.

What happened at Yoyogi Park

In late August 2014, three people who hadn't traveled abroad were diagnosed with dengue, all bitten in Yoyogi Park, a forested park in central Tokyo. It was Japan's first locally acquired dengue in nearly 70 years. By September 17, WHO's Western Pacific surveillance journal counted 131 locally acquired cases from 17 of Japan's 47 prefectures, 112 of them linked to Yoyogi Park or its vicinity, all dengue type 1 and none fatal. Final tallies put the outbreak at about 160 cases.

Tokyo's government had tested mosquitoes from 16 sites since 2004, and that September brought the first positives, in Yoyogi Park and then in Shinjuku Gyoen, about 1.2 miles (2 km) away. Both parks were closed. A later modeling study found that mosquito control and public warnings alone didn't stop transmission until the closures were added.

A CDC journal analysis of 2011–2016 surveillance found no other epidemic and called Yoyogi probably an unusual event. We know of no outbreak in Tokyo since. Imported cases still arrive with travelers, rising each August and September, and the mosquito that spread the 2014 virus is common in the city.

Tiger mosquitoes in the shrine forests

The tiger mosquito, Aedes albopictus, bites by day with peaks in the morning and late afternoon, and it favors shade. Researchers have found it at higher densities in Tokyo than in its suburbs. In Yoyogi Park in September 2014, entomologists from Japan's national infectious disease institute measured an average of 7.13 bites per person in 8 minutes, a rate they called high enough for dengue transmission.

So the routine centers on green spaces. Put repellent on over sunscreen before Yoyogi Park, Meiji Jingu, Shinjuku Gyoen or any shrine, temple or garden, and reapply before a late-afternoon or dusk walk. Shady, still spots near plants or water tend to be the worst. Our picaridin vs. DEET comparison helps you choose a repellent.

The vaccine question

Japanese encephalitis is present in Japan, with very few human cases. A Tokyo stay fits what CDC calls "short-term travel to urban areas," and for that the vaccine is "Not recommended." Sightseeing day trips aren't the rural stays, camping or unscreened lodging where CDC says to "Consider vaccination." Several days of hiking or camping in the mountains, a month or more in Japan, or a move there are worth a travel-clinic visit 4–6 weeks before departure, and our Japan briefing covers the countryside. No malaria medicine or yellow fever vaccine is needed. CDC also lists tick-borne encephalitis for Japan, so check for ticks after forest trails.

When the bites come

Tiger mosquitoes start biting between April and June and stay active until about November. The rainy season and the humid heat of July and August bring the most bites. Late August and September deserve the most care in parks, since the 2014 outbreak ran from August into early October. A spring visit falls before the peak, an autumn trip to the gardens still calls for repellent, and from December to March bites essentially stop.

Where you're going

Flying on to the subtropical south? Our Okinawa briefing covers islands where tiger mosquitoes bite all year.

What travelers report

Paraphrased from TripAdvisor forum threads and linked so you can read them in full. Only one is dated, to 2025, and one also covers Kyoto, so read them for where and when bites happen.

• Tokyo · 2025

  A UK traveler worried about bites got 14 replies: use a DEET repellent rather than 'natural' products and buy it at a drugstore after arriving; dusk in dark, windless spots near plants or water is the worst time; in the city the risk is mainly at shrines, temples and gardens; antihistamines, steroid creams or the Japanese itch cream Muhi help. TripAdvisor ↗

• Central Tokyo

  A UK visitor with four bites after a few nights in Tokyo asked whether central Tokyo's mosquitoes posed any real danger. Replies were reassuring: one said the disease risk from a bite was negligible and that any outbreak would make the local news, another that steroid cream works quickly and bites usually fade within a day or two. TripAdvisor ↗

• Hakone and Kyoto

  A poster said they were bitten in Hakone and around Kyoto by large striped mosquitoes and warned that the bites can blister without quick treatment. TripAdvisor ↗

• Japan (city parks and gardens) · summer

  Answering a question about summer mosquitoes, a poster advised using repellent mainly in the evening and in shady or bushy spots such as park restrooms and bamboo groves, and said bites from the small striped mosquitoes itch for a while. TripAdvisor ↗

One rule outlasts the trip. Any fever during your trip or in the two weeks after it means a doctor visit, and you tell them about mosquito bites in Japan and any other country on your route.

Traveler questions