What is a key characteristic of COVID-19?

The key characteristic of COVID-19 is that it primarily affects the respiratory system. This is due to the fact that the virus, known as SARS-CoV-2, primarily enters the body through the respiratory tract and can lead to symptoms such as coughing, difficulty breathing, and pneumonia, which are all related to respiratory function. Understanding how COVID-19 primarily impacts the respiratory system helps inform treatment approaches and public health policies for controlling its spread.

The other options do not accurately capture the primary characteristics of COVID-19. While the virus can have serious consequences, it does not have a uniformly high fatality rate across all age groups; older adults and those with underlying health conditions are at greater risk. Furthermore, COVID-19 is not identified as a skin disease, as its main symptoms and health complications arise from its effects on the respiratory system. Lastly, the virus spreads through various modes, including respiratory droplets, aerosols, and surfaces, not solely through physical contact. Thus, the most defining feature of COVID-19 is its significant impact on respiratory health.