COVID 19 refers to a class of viruses that infect mammals and birds. Coronavirus causes respiratory infections in humans. The symptoms of this infection can be mild, often resembling the common cold (there may be other causes, such as rhinovirus), in some cases it is caused by other deadly viruses, such as SARS, MARS and COVID-19. Other species have different symptoms. As in chickens, it causes upper respiratory tract infections, and in cows and pigs, it causes diarrhea. To date, no vaccines or antiviral drugs have been developed to prevent coronavirus infections in humans. However, the United Kingdom has discovered a vaccine that makes the coronavirus more diverse in terms of the potential for harm. Some variants kill more than 30% of the infected (e.g. Mars-Cove), some variants are fairly innocuous, such as the common cold. [21] Coronavirus causes cold as well as some major symptoms, such as fever, sore throat due to swollen adenoids. These usually occur in winter and early spring40] Coronavirus can cause pneumonia (directly viral pneumonia or indirectly bacterial pneumonia) and bronchitis (directly viral bronchitis or indirectly bacterial bronchitis)41] Coronavirus has been known since the outbreak of SARS-covine in 2003. The virus also causes severe acute respiratory syndrome (SARS) and upper and lower respiratory tract infections.