Until the early part of the twentieth century many vector-and rodent-borne infections were very serious public health problems in Europe and North America. Thousands of cases of malaria occurred annually throughout these regions and populations suffered greatly from the disease. Malaria transmission persisted in most of southern Europe and the USA until it was eradicated in the 1950s. Among the arboviruses, dengue transmitted by the mosquito Aedes aegypti, was the cause of a great epidemic in Athens, Greece in 1928 with over 650 000 cases and more than a thousand deaths. The same species was also the vector of yellow fever which caused many thousands of deaths in the USA during the nineteenth century; the last epidemic of the disease occurred in New Orleans in 1905 with more than 3000 cases and at least 452 deaths being recorded. Great epidemics of louse-borne typhus occurred in many parts of Europe during World War I accounting for great human mortality. The war-associated louse-borne diseases such as epidemic typhus, epidemic relapsing fever and trench fever disappeared after 1945 due to the applications of the newly discovered DDT and related compounds; at the time, optimism ran high that this group of infections was unlikely to again be a problem, and indeed at the time effective control was obtained of most of the group.