We must breath in oxygen so cellular respiration can occur and our cells can gain more ATP (energy) to function.
Cells need energy from the food we eat to to do it’s job such as beating the heart, but the cells cannot work without energy from cellular respiration. Cellular respiration requires glucose and oxygen to create carbon dioxide, water, and ATP.
Influenza virus can exhibit constant mutation of viral glycoproteins, called antigenic , or alternatively antigenic , which is a more serious phenomenon caused by the exchange of a viral gene with that of another influenza virus strain.