The Greek Authorities report a resurgence of the West Nile Virus (WNV) due to climatic conditions favourable to the propagation of mosquitoes transmitting the virus. Up to now 153 cases have been identified resulting in 17 deaths in Greece. The Greek Health Authorities follow the situation.
General precaution measures:
Besides the medicaments that are normally needed, the travelers should have with them insect repellents, preferably containing DEET (diethyltoluamide), strictly following the user instructions. They should wear light-coloured clothes covering most of their body.
For more information you can consult the W.H.O. – World Health Organization site in English http://www.euro.who.int/en/health-topics/communicable-diseases/vector-borne-and-parasitic-diseases/news/news/2018/8/west-nile-virus-infections-spike-in-southern-and-central-europe.