Every human virus is of animal origin,very often by bats or birds.
SARS-CoV-2
(severe acute respiratory syndrome coronavirus 2)
Severe acute respiratory syndrome
COVID-19
(Corona Virus Disease 2019)
Corona virus disease 2019
Source: https://www.youtube.com/watch?v=NU31mw90re0&feature=emb_logo
Things explained – Kurzgesagt, an offer from Funk
Source: Federal Center for Health Education (BZgA), infektionsschutz.de,https://www.infectionprotection.de/mediathek/filme/corona-knowledge-compact.html#c13360, CC BY-NC-ND
The infected cells are destroyed and the Organ functions become restricted such as difficulty breathing, coughing, loss of smell.
The body releases messenger substances.
D
The messenger substances report the invasion of a virus to the body.
This is followed by a
Immune reaction
or
Inflammatory reaction
such as fever, weakness, etc.
The occurrence of a contagious disease (infectious disease) is classified depending on its extent into:
Spread across entire continents or worldwide
(e.g. Covid-19, “Spanish flu”)
Limited in time and place
(e.g. seasonal flu, plague in the Middle Ages in Europe)
Persistent occurrence within a specific geographical region (e.g. malaria in tropical countries)