Contagious disease

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A contagious disease is an infectious disease that can be spread rapidly in several ways, including direct contact, indirect contact, and Droplet contact. ^[1]

These diseases are caused by organisms such as parasites, Bacteria, Fungi, and viruses. While many types of organisms live on the human body and are usually harmless, these organisms can sometimes cause disease. ^[2]

Some common infectious diseases are Influenza, COVID-19, Ebola, hepatitis, HIV/AIDS, Human papillomavirus infection, Polio, and Zika virus. ^[3]

A disease is often known to be contagious before medical science discovers its causative 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 by bacteria. Microbial pathogenesis attempts to account for diseases caused by a virus.