## Infectious levels [Infection](https://ul.orna.me/KOge/librarydisease?id=32) requires a certain infectious dose (viral load), which is the smallest amount of virus that can cause infection. The larger the dose of the virus a person receives, the greater the infection burden and therefore the more severe the disease. This applies to all respiratory diseases. For example, if a person came into a room where someone else sneezed for a few minutes, the person’s immunity has a better chance to cope with the virus than if he or she was in contact with a sick person for a long time. Scientists have determined that each cell infected with coronavirus contains about 10 viral particles called virions. In total, a person infected with COVID-19 in an acute period carries between one billion to one hundred billion units of the virus. ## What does the degree of contagiousness depend on? The contagiousness of an infected person is directly proportional to the level of his or her viral load: low, medium, or high. The virus multiplies especially intensively 1–3 days before and during the first 5–7 days after the appearance of disease symptoms. Generally, the viral load decreases from 7–10 days after the onset of clinical manifestations, and the person is no longer contagious. ## Risk factors What influences the load level that will infect a person? - Immunity - Chronic diseases: diabetes, respiratory diseases, diseases of the cardiovascular system, - Age: the older the person, the greater the risk - The distance from which the infection occurred: the larger space and the more dispersed the virus is, the lower its concentration - The time the virus has been on the surface: the more time has passed, the weaker it will become ## Asymptomatic but dangerous In the case of [COVID-19](https://ul.orna.me/KOge/librarydisease?id=221), it is important to remember that clinical manifestations of the disease may be absent at any level of viral load. It may be that the PCR is positive and the viral load level is high, but the disease is asymptomatic. In this case, you need to take all safety precautions and not put others at risk.