During the 17th and 18th centuries, measures were taken by the Venetian administration to combat plague on the Ionian Islands. At that time, although the scientific basis of plague was unknown, the Venetians recognized its infectious nature and successfully decreased its spread by implementing an information network. Additionally, by activating a system of inspection that involved establishing garrisons along the coasts, the Venetians were able to control all local movements in plague-infested areas, which were immediately isolated. In contrast, the neighboring coast of mainland Greece, which was under Ottoman rule, was a plague-endemic area during the same period. We conclude that even in the absence of scientific knowledge, close observation and social and political measures can effectively restrain infectious outbreaks to the point of disappearance.
The Venetian health policy was reformed in the 18th century. These reforms likely emphasized disease prevention and dealt with health emergencies (17). The new policy was based on daily reports of health conditions on the islands and suspicious areas in the eastern Mediterranean, and included creation of a common public health framework (identical laws for plague control, decrees, and institutions and infrastructures) for all islands.
Despite these new regulations, Venetian archives reported occasional problems in health services of the islands because of poorly trained health officers, who were elected from the local upper class and were eager to acquire greater political autonomy.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660681/