According to the "very cautious" estimate of Dr. Ashkup - Chairman of the Doctorate of Doctors with Infectious Diseases, the Medical Academy (Singapore), each person with COVID-19 can infect at least 3 or 4 others. In fact, the transmission mechanism of this virus is more similar to H1N1 or flu than SARS. It can be transmitted as soon as the symptoms are still mild, even those who have no symptoms (no signs of illness). This means that these people can spread the virus before it becomes undetected. Therefore, the number of COVID-19 infections continues to increase, an "unprecedented spread". Wearing a mask is an essential measure to help prevent the disease caused by corona virus. “The large number of people who do not have symptoms or have secondary symptoms, such as the common cold, may be 4 times more likely than the number of patients we currently see. They are the ones who spread the virus ”, Dr. Leong Hoe Nam (Warning: Mount Elizabeth Novena Expert Center) warns. International tourism is the main reason for the rapid spread of the epidemic Although soon after the WHO issued the warning that COVID-19 was an urgent public health condition of international concern, many countries had suspended and restricting flights to and from China. However, this is still not enough to prevent the spread of disease. To put it more simply, a lot of people infected with COVID-19 but without symptoms around the world may still be traveling and the transmission of the disease is quite possible. Since the new strain of corona virus (COVID-19) has never been identified before, the stages of infection are still in the research phase, so each individual should actively protect himself and his family by fully implementing preventive measures as recommended by the Ministry of Health.