Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Take a deep breath in …and out. Feels good, right? And it's also necessary for staying alive. But what ...

RTIs affect the respiratory system, from nose and throat to lungs. Viruses and bacteria cause RTIs; symptoms include cough, fever, and sore throat. Handwashing, vaccination, and avoiding sick people ...