I work for County Vector Control (Mosquito abatement-health) here in So. Cal and travel often to Europe/Eastern Europe in my summers.
Mosquitoes in wooded areas are at times quite heavy-they will feed both day and night hours. Mosquitoes rest during the day under the leaves of plants and are attracted to carbon dioxide given off by mammals. On hikes in Ukraine my son and I would pass through a damp shaded area and start to run through (laughing of course) because of the number of mosquitoes that lighted on us in an area. Ticks-as mentioned-'tick borne encephalitis' indeed has been a concern. Black Flies are the worst-they cause a large red bump at times and a real good itch.
I'd still go in a heartbeat! Bring a mosquito net for sleeping.