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Acontagious disease is aninfectious disease that can be spread rapidly in several ways, including direct contact, indirect contact, anddroplet contact.[1][2]
These diseases are caused by organisms such asparasites,bacteria,fungi, andviruses. While many types of organisms live on the human body and are usually harmless, these organisms can sometimes cause disease.[3]
Some common infectious diseases areinfluenza,COVID-19,ebola,hepatitis,HIV/AIDS,Human papillomavirus infection,Polio, andZika virus.[4]
A disease is often known to be contagious beforemedical science discovers itscausative agent.Koch's postulates, which were published at the end of the 19th century, were the standard for the next 100 years or more, especially with diseases caused bybacteria.Microbial pathogenesis attempts to account for diseases caused by avirus.
Originally, the term referred to acontagion or disease transmissible only by direct physical contact. In the modern-day, the term has sometimes been broadened to encompassany communicable or infectious disease. Often the word can only be understood in context, where it is used to emphasize veryinfectious, easily transmitted, or especially severe communicable diseases.
In 1849,John Snow first proposed that cholera was a contagious disease.
Mostepidemics are caused by contagious diseases, with occasional exceptions, such asyellow fever. The spread of non-contagious communicable diseases is changed either very little or not at all by medical isolation of ill persons or medicalquarantine for exposed persons. Thus, a "contagious disease" is sometimes defined in practical terms, as a disease for which isolation or quarantine are useful public health responses.[5][failed verification]
Some locations are better suited for the research into the contagious pathogens due to the reduced risk of transmission afforded by a remote or isolated location.
Thebasic reproduction number of a disease is used to measure how easily the disease spreads through contact with infected individuals.
Negative room pressure is a technique in health care facilities based onaerobiological designs.
A primer from the CDC on quarantine and its uses against contagious disease spread
