Covid-19 is an infectious disease caused by a new novel virus. The disease causes respiratory illness (similar to the flu), with symptoms such as cough, fever, and in more severe cases, difficulty breathing. Since its discovery in 2019, it have rapidly spread around the globe. Many policies were implemented such as social distance and quarantine. These policies were based on evidence from diverse SEIR's models, which shown an exponential grown rate in many countries.


Infection with this virus occurs when it enters the body through the mouth, nose, or even the eyes. This usually happens, when an infected person coughs, sneezes, talks, sings or breathes, spreading the virus through the air in the form of particles. Therefore when a person is close to such particles, the virus will enter the body. There are also some additional infectious factors, such as the virus payload, the exposure time, the health of the exposed person, etc. In any case, it is still recommended to wear a mask and avoid unnecessary social gatherings to lower the exposure to possible infecctions.


Among the effects on the body, SARS-CoV-2 can seriously damage different organs of the body, including the lungs. However, with rehabilitation therapies it is possible to repair the damage to the organs. Studies have shown different incubation periods, which vary with each virus variant.


Some patients developed severe acute respiratory syndrome, which presents with fever and difficulty breathing. There is also a sharp pain in the upper and lower areas of the lungs. In some cases, a patient may not develop visible symptoms. Due to this peculiarity, patients are usually classified as symptomatic (with symptoms) and asymptomatic (without symptoms). It should be clarified that the fact of not developing visible symptoms does not mean that a patient is immune to the virus.