1, infected contact population
COVID-19 is a highly contagious disease. If the patient is infected with COVID-19 and is not isolated in time, it is easy to infect the contacts, resulting in the spread from person to person. Novel coronavirus usually uses droplets and contact as one of the main modes of transmission. If you are in the same environment as COVID-19 patients, the virus can easily spread among people through the respiratory tract, and the probability of infection will be very high. At the same time, novel coronavirus has a long incubation period, which is also contagious. The long incubation period may also lead to infection in many susceptible people. At present, there are relatively many susceptible people, such as the elderly or people with obvious primary diseases, and their immunity is relatively poor, so they belong to susceptible people in COVID-19.
2. Irreversible damage to the lungs of infected people.
COVID-19's effect on the lungs depends on the severity of pneumonia. Novel coronavirus can be divided into asymptomatic patients, mild patients and severe or critical patients according to the severity of the disease. Such as asymptomatic patients or mild patients, there may be mild or asymptomatic. Confirmed patients only need to undergo certain isolation treatment, and the results of nucleic acid tests on both sides are negative after an interval of more than 24 hours, so they are no longer contagious, and patients can recover, with little special impact on patients' lungs. If the patient suffers from severe COVID-19's disease or even critical illness, the patient's lungs will usually be fibrotic and may have symptoms of respiratory failure, which will cause irreversible damage to the lungs and even life-threatening, so it is necessary to give ventilator treatment in time. Even after the patient is cured, the lung function will be affected to varying degrees.