Marcus Terentius Varro

Marcus Terentius Varro Reatinus (116 – 27 BC) was a Roman writer. He wrote many books, but only one work survives completely - "Three books on Agriculture". In this work, he describes farming in Roman times. 
Scholars say this book has a little microbiology and epidemiology. Varro warned his contemporaries to stay away from swamps and marshes: 
...there are bred certain minute creatures which cannot be seen by the eyes, but which float in the air and enter the body through the mouth and nose and cause serious diseases.