Dengue fever originated in the tropics. However, for a few years now it has also been found in other warm regions of the world, such as the Mediterranean. Scientists are attributing this to climate change: the mosquitoes that transmit the virus to humans are able to expand their habitat thanks to increasing global warming. Back in 2010, the Robert Koch Institute reported on dengue fever in southern France and Croatia. In Germany in 2013, there were a total of 879 recorded dengue patients – all travelers who had become infected in the southern hemisphere and in tropical countries. The World Health Organization (WHO) estimates that the number of infections globally stands at 390 million a year. In 1970, infections occurred in just nine countries. These days, that figure has already risen to over 100.