who discovered that infectious disease was spread by bacteria
Germ theory of disease The germ theory was proposed by Girolamo Fracastoro in 1546, and expanded upon by Marcus von Plenciz in 1762. Such views were held in disdain, however, and Galen's miasma theory remained dominant among scientists and doctors. The nature of this doctrine prevented them from understanding how diseases actually progressed, with predictable consequences. By the early nineteenth century, smallpox vaccination was commonplace in Europe, though doctors were unaware of how it worked or how to extend the principle to other diseases. Similar treatments had been prevalent in India from just before AD 1000.[2] [N 1] A transitional period began in the late 1850s with the work of Louis Pasteur. This work was later extended by Robert Koch in the 1880s. By the end of the 1880s the miasma theory was struggling to compete with the germ theory of disease. Eventually, a "golden era" of bacteriology ensued, during which the theory quickly led to the identification of the actual organisms that cause many diseases.[3][4] Viruses were discovered in the 1890s.
Ebola virus disease The virus spreads through direct contact with body fluids, such as blood from infected humans or other animals.[1] Spread may also occur from contact with items recently contaminated with bodily fluids.[1] Spread of the disease through the air between primates, including humans, has not been documented in either laboratory or natural conditions.[3] Semen or breast milk of a person after recovery from EVD may carry the virus for several weeks to months.[1][4][5] Fruit bats are believed to be the normal carrier in nature, able to spread the virus without being affected by it.[1] Other diseases such as malaria, cholera, typhoid fever, meningitis and other viral hemorrhagic fevers may resemble EVD.[1] Blood samples are tested for viral RNA, viral antibodies or for the virus itself to confirm the diagnosis.[1]