If a patient with C. neoformans is positive for IgM antibodies, it is likely to be contagious. Neocoronavirus pneumonia is an acute respiratory infectious disease caused by a novel coronavirus infection, which is highly contagious. However, whether or not it is contagious has less to do with whether or not the patient’s body is antibody-positive, and more to do with whether or not the patient is able to expel the neocoronavirus, for example, if there is a certain number of neocoronaviruses present in the respiratory mucous membranes, the infection can spread through droplet transmission. There are two types of antibodies to neocoronaviruses, IgM and IgG, of which IgG positivity indicates infection with neocoronaviruses, but the presence of acute infection needs to be judged in conjunction with a nucleic acid test, while IgM positivity generally indicates acute infection, that is, the presence of a significant amount of neocoronaviruses in the body, including in the respiratory tract, in the lungs, and in the bloodstream, and is therefore most likely infectious, especially if there are clinical symptoms, requiring further investigation. Those with clinical symptoms require further nucleic acid testing.