Doctors once believed that illness was caused by foul air and could not be transmitted from one person to another. Now, doctors know that single-celled bacteria and even smaller viruses cause illnesses and can be transmitted from one person to another. How did the advent of the microscope most likely affect the foul-air theory?

Microscope use to observe microscopic organisms such as bacteria, viruses, and others. The spontaneous observation that microorganisms move and transport through the air which serves as their medium or channel to transfer from one place to another. This microbiology or study with the use of the microscope greatly affects and contributed to the foul air theory on which traces of the sources of disease became the focus of their study. Diseases and properties of microorganisms, as well as, the solution on how to cure and fight these becomes possible with the availability of microscope.