Although viruses, mycoplasma, rickettsiae and fungi can all cause lower respiratory tract infections, bacteria are the dominant pathogens; accounting for a much higher percentage of lower than of upper respiratory tract infections. (National Center for Biotechnology Info)

COVID-19 is a disease that can cause what doctors call a respiratory tract infection. It can affect your upper respiratory tract (sinuses, nose, and throat) or lower respiratory tract (windpipe and lungs). (WebMD)

Respiratory tract infections are the most common cause of hospital admissions and death in NMD patients with respiratory muscle involvement. (Science Direct)