Istanbul is lighter than the coast. Evenings by the water still call for repellent.

Yes, though fewer than on Türkiye's Aegean and Mediterranean coasts. Istanbul's house mosquitoes come out at dusk and fly in through open windows at night, and in 2024 they spread West Nile to 44 people in the city, with none listed by the European Centre for Disease Prevention and Control (ECDC) since. CDC recommends no malaria medicine for Türkiye, so a small spray for evenings and a closed window at night cover most of it.

Two West Nile summers

West Nile travels on Culex pipiens, the house mosquito, which bites from dusk through the night. Istanbul had its first documented outbreak in 2019, and in 2024 Türkiye had its largest. ECDC listed 90 locally acquired cases and 7 deaths in the country, 44 of the cases in Istanbul. It listed none in the city in 2025, when Türkiye's only case was in Çanakkale, and Türkiye doesn't appear in its 2026 tables through October 21, which may mean no cases or no reporting. Our Türkiye briefing covers the rest of the country.

A 2025 study of Istanbul Health Directorate data counted 159 reported cases from 2010 to 2024. Even in the two outbreak years, the rate was about 0.5 cases per 100,000 people. Every case began between June and October, and the 2019 outbreak peaked in July and the 2024 one in August. There is no vaccine, and older travelers face the most risk of severe illness, so evening repellent is the protection.

No locally acquired dengue, chikungunya or Zika has been reported in Türkiye, and the last locally acquired malaria was in southeastern Anatolia in 2009. CDC lists no malaria medicine for Türkiye and says of yellow fever, "Vaccine is not recommended" and "Vaccine is not required." It also lists leishmaniasis, spread by sand flies that bite from dusk to dawn and concentrated in the southeast and the Mediterranean region, and a tick-borne disease of rural Anatolia, far from Istanbul.

Bosphorus evenings and a new daytime biter

The tiger mosquito, a small, striped daytime biter, was first found in Türkiye in 2011, in Thrace near the Greek border. ECDC's April 2026 map now shades Istanbul as established. It bites in parks, gardens and shady courtyards, with peaks in the morning and late afternoon. The other invasive species, Aedes aegypti, appears on the same maps only on the far northeastern Black Sea coast.

The likeliest bites come at waterside dinners along the Bosphorus in Ortaköy, Bebek and Kuzguncuk, on garden terraces on the Princes' Islands, on walks in the Belgrad Forest, and in older hotel rooms without screens when the window stays open at night. A day in Sultanahmet among the stone monuments tends to bring few. From July to September, put repellent on before evening dinners and rooftop drinks, add a daytime coat for park and garden afternoons, and keep the window shut or a plug-in vaporizer running at night. Our repellent timing guide shows how long a coat lasts.

June tends to be the easiest summer month. Late July to September is when West Nile has occurred and when warm nights mean open windows. Spring tends to be mild, and an October trip still falls inside the June-to-October window in which every recorded case began.

Where you're going

How the main parts of an Istanbul stay compare for a June–September trip.

Heading south afterward? The Antalya briefing covers the Riviera's sand flies, and the Bodrum briefing covers the Aegean coast and Ephesus.

What travelers report

Paraphrased from TripAdvisor threads and linked so you can read them in full. Neither is dated or describes an outbreak summer, and bites depend a lot on your room and whether the window stays shut.

• Istanbul · late July to early August

  A traveler who reacts strongly to bites asked whether to pack repellent for a late July to early August trip; a reply said bringing it is the safe choice for anyone allergic to bites, but that in a fairly developed city like Istanbul they would most likely see few or no mosquitoes. TripAdvisor ↗

• Istanbul · May

  Asked whether there are mosquitoes in Istanbul in May, one reply expected conditions to be mild at that time of year and suggested buying repellent in local shops, naming the Sinkov and Off brands; another answered simply that it was unlikely. TripAdvisor ↗

One rule outlasts the trip. A fever with headache, a stiff neck or confusion during or within two weeks after the trip means a doctor visit, and so does a skin sore that won't heal. Tell the doctor you were in Istanbul.

Traveler questions