Unique infectious profile explains why it is so hard to treat COVID-19 A comprehensive review into what we know about COVID-19 and the way it functions suggests the virus has a unique infectious profile, which explains why it can be so hard to treat and why some people experience so-called "long-COVID", struggling with significant health issues months after infection. There is growing evidence that the virus infects both the upper and lower respiratory tracts - unlike "low pathogenic" human coronavirus sub-species, which typically settle in the upper respiratory tract and cause cold-like symptoms, or "high pathogenic" viruses such as those that cause SARS and ARDS, which typically settle in the lower respiratory tract.