The Collaborative International Dictionary
Respiratory tree
Respiratory \Re*spir"a*to*ry\ (r?*sp?r"?*t?*r? or r?s"p?*r?-), a. (Physiol.) Of or pertaining to respiration; serving for respiration; as, the respiratory organs; respiratory nerves; the respiratory function; respiratory changes.
Respiratory foods. (Physiol.) See 2d Note under Food, n., 1.
Respiratory tree (Zo["o]l.), the branched internal gill of certain holothurians.
Usage examples of "respiratory tree".
Obviously it is an airborne infection, but it usually invades the upper part of the respiratory tree, not the lungs.