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Viral pathogenesis is the study of the process and mechanisms by which viruses cause diseases in their target hosts, often at the cellular or molecular level. It is a specialized field of study in virology. [1] Pathogenesis is a qualitative description of the process by which an initial infection causes disease. [2]
The human coronavirus NL63 shared a common ancestor with a bat coronavirus (ARCoV.2) between 1190 and 1449 CE. [76] The human coronavirus 229E shared a common ancestor with a bat coronavirus (GhanaGrp1 Bt CoV) between 1686 and 1800 CE. [77] More recently, alpaca coronavirus and human coronavirus 229E diverged sometime before 1960. [78]
The relationship between virulence and transmission is complex and has important consequences for the long term evolution of a pathogen. Since it takes many generations for a microbe and a new host species to co-evolve, an emerging pathogen may hit its earliest victims especially hard.
Neither of these colonizations are considered infections. The difference between an infection and a colonization is often only a matter of circumstance. Non-pathogenic organisms can become pathogenic given specific conditions, and even the most virulent organism requires certain circumstances to cause a compromising infection.
Furin cleavage contributes strongly to the transmissibility and pathogenicity of SARS-CoV-2 in humans. [28] SARS-CoV-2 variants lacking the furin cleavage site are transmissible between humans, but much less effectively. [29] The furin cleavage site is sometimes described as "polybasic" on account of its particular motif of basic amino acids. [28]
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.
The transmission of COVID-19 is the passing of coronavirus disease 2019 from person to person. COVID-19 is mainly transmitted when people breathe in air contaminated by droplets/aerosols and small airborne particles containing the virus. Infected people exhale those particles as they breathe, talk, cough, sneeze, or sing.
In particular, pathogenic bacteria are capable of translating virulence genes located within their plasmids into different virulence factors in order to aid the bacterium in pathogenesis. [3] Many different types of virulence factors exist within pathogens, including: adherence factors, invasion factors, capsules, siderophores , endotoxins ...