who came up with the germ theory of disease
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 1000 A.D.[2] [N 1] A transitional period began in the late 1850s as the work of Louis Pasteur and Robert Koch provided convincing evidence; by 1880, 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.
Typhoid fever The cause is the bacterium Salmonella Typhi, also known as Salmonella enterica serotype Typhi, growing in the intestines and blood.[2][6] Typhoid is spread by eating or drinking food or water contaminated with the feces of an infected person.[4] Risk factors include poor sanitation and poor hygiene.[3] Those who travel to the developing world are also at risk[6] and only humans can be infected.[4] Diagnosis is by either culturing the bacteria or detecting the bacterium's DNA in the blood, stool, or bone marrow.[2][3][5] Culturing the bacterium can be difficult.[10] Bone marrow testing is the most accurate.[5] Symptoms are similar to that of many other infectious diseases.[6] Typhus is a different disease.[11]