Coronavirus diseases are caused by viruses in the coronavirus subfamily, a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, the group of viruses cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the common cold (which is also caused by other viruses, predominantly rhinoviruses), while more lethal varieties can cause SARS, MERS and COVID-19. As of 2021, 45 species are registered as coronaviruses, whilst 11 diseases have been identified, as listed below. Coronaviruses are known for their shape resembling a stellar corona, such as that of the Sun visible during a total solar eclipse; corona is derived from the Latin word corōna, meaning garland, wreath, crown. It was coined by Tony Waterson (professor of virology at St Thomas Hospital) in a meeting with his colleagues June Almeida and David Tyrrell, the founding fathers of coronavirus studies, and was first used in a Nature article in 1968, with approval by the International Committee for the Nomenclature of Viruses three years later.The first coronavirus disease was discovered in the late 1920s, however, the most recent common ancestor of coronaviruses is estimated to have existed as recently as 8000 BCE. Human coronaviruses were discovered in the 1960s, through a variety of experiments in the United States and the United Kingdom. A common origin in human coronaviruses is bats. List
See also

Coronaviridae
Alphacoronavirus
Betacoronavirus
Gammacoronavirus
Deltacoronavirus
Novel coronavirus (nCoV)


== References ==
Both the modified zinc sulfate centrifugal flotation technique and the Sheathers sugar flotation procedure can concentrate the oocysts by causing them to float. Another form of microscopy is fluorescent microscopy done by staining with auramine.Other staining techniques include acid-fast staining, which will stain the oocysts red. One type of acid-fast stain is the Kinyoun stain. Giemsa staining can also be performed. Part of the small intestine can be stained with hematoxylin and eosin (H & E), which will show oocysts attached to the epithelial cells.Detecting antigens is yet another way to diagnose the disease. This can be done with direct fluorescent antibody (DFA) techniques. It can also be achieved through indirect immunofluorescence assay. Enzyme-linked immunosorbent assay (ELISA) also detects antigens.Polymerase chain reaction (PCR) is another way to diagnose cryptosporidiosis. It can even identify the specific species of Cryptosporidium. If the patient is thought to have biliary cryptosporidiosis, then an appropriate diagnostic technique is ultrasonography. If that returns normal results, the next step would be to perform endoscopic retrograde cholangiopancreatography. Prevention
Many treatment plants that take raw water from rivers, lakes, and reservoirs for public drinking water production use conventional filtration technologies. This involves a series of processes, including coagulation, flocculation, sedimentation, and filtration. Direct filtration, which is typically used to treat water with low particulate levels, includes coagulation and filtration, but not sedimentation. Other common filtration processes, including slow sand filters,  diatomaceous earth filters and membranes will remove 99% of Cryptosporidium.