The Danube Delta bites hardest. Bucharest has Romania's West Nile.

Yes, and where you go decides how many. The Danube Delta is notorious for mosquitoes on summer evenings, Bucharest and the Black Sea coast have moderate evening mosquitoes, and Transylvanian towns like Brașov and Sibiu see few. The health item is West Nile virus, which Romania reports every summer. The country had 125 cases in 2026 as of October 21, 45 of them in Bucharest.

The Danube Delta after dark

For a few hours each evening, mosquitoes and biting flies are a given on Delta boat trips and at the village lodges around Tulcea, Murighiol and Sulina. The numbers back up the reputation. In 2014, researchers trapping at four Delta sites, among them Sulina, Letea and Lake Roșuleț, caught 240,546 female mosquitoes in carbon-dioxide traps. Catches peaked in early June, with further peaks at the end of June and in August, so an early-summer trip lands in the thick of it.

Dress for the evening. Wear long sleeves and long pants on boat trips and at lodge dinners, treat that clothing with permethrin (fabric only, never skin), reapply repellent from late afternoon and sleep in a screened or air-conditioned room. Romania has been malaria-free since WHO certified it in 1967, and CDC recommends no malaria medicine anywhere in the country.

West Nile, centered on Bucharest

West Nile is spread by Culex house mosquitoes, which bite in the evening and at night. The European Centre for Disease Prevention and Control (ECDC) counted 125 locally acquired cases in Romania in 2026 as of October 21, well above 2025's 49 and in line with 2023 (103) and 2024 (99), with 7 deaths through October 7. Bucharest had 45 of the cases, neighboring Ilfov and Giurgiu 12 each, and most of the rest came from counties in the south and southeast. The 2018 season was far bigger, with 277 cases and 43 deaths, according to an analysis in the journal Eurosurveillance.

For a Bucharest city break from July to September, put repellent on before evenings in parks, by lakes such as Herăstrău and on terraces. Severe illness falls mostly on people 65 and older, and there is no vaccine, so older travelers and anyone with a weakened immune system should take the dusk routine most seriously. Our guide to how long repellent lasts helps you time the evening top-up. A May trip comes before the West Nile season, which runs from June into October.

Transylvania and the Black Sea coast

Transylvania is the easy part, with few bites in Brașov, Sibiu and Sighișoara and few West Nile cases. On the coast, Constanța county had 2 cases in 2026, and evening mosquitoes are the issue around Constanța and Mamaia, where hotel reviews mention them coming in through balcony doors without screens. Ask for a screened room or keep the door shut after dark.

The tiger mosquito, a day biter with peaks in the morning and late afternoon, is established in 10 of Romania's 42 regional units, on ECDC's April 2026 map. Romania has never reported a locally acquired case of dengue or chikungunya, both of which this mosquito can spread. CDC also lists leishmaniasis, spread by sand flies that bite from dusk to dawn, though cases in Romania are rare.

Where you're going

How the main stops compare for a June–September trip.

Crossing the Danube to the south? Our Bulgaria briefing covers Varna and Sunny Beach. Upriver, our Serbia and Hungary briefings cover Belgrade, Budapest and the Danube cruise stops.

What travelers report

Paraphrased from TripAdvisor forum threads and a review and linked so you can read them in full. None is dated to this season, and an evening in the Delta or in Bucharest changes a lot with the weather and where you stay.

• Danube Delta · June

  Answering a question about weather and bugs on a June Delta trip, a reply said mosquitoes and biting flies are a problem for only 2-3 hours a day, mainly in the evening, and advised repellent and long clothing. Another reply said the mosquitoes come out at night, from about 8 pm. TripAdvisor ↗

• Bucharest

  A poster found Bucharest surprisingly bad for bites: they and a friend were bitten heavily there, while Brașov, Sibiu, Constanța and Sighișoara seemed free of mosquitoes. A reply said visitors who stick to regular areas will be fine but should take care around lakes such as Herăstrău. TripAdvisor ↗

• Brașov

  A Brașov resident said they had not been bitten in six years in Brașov, but were bitten regularly in Bucharest. TripAdvisor ↗

• Domeniul Greaca (Giurgiu county, about an hour from Bucharest)

  A reviewer described one night of heavy mosquito activity, with tens of bites, some of them indoors. TripAdvisor ↗

And the rule that outlasts every trip: any fever during or after your trip means a doctor visit, and you tell them you were in Romania.

Traveler questions