COVID-19
Scientists looked at the lungs from people who died of COVID-19.  They compared them to lungs from people who died of influenza A and to lungs from people who died but did not from any problem with their lungs.  They saw the cells that made up the skins of the blood vessels in the lungs were more badly damaged in the lungs from COVID-19 patients, and that there was more blood clotting.  The most important difference the scientists saw was that the lungs had begun to grow new blood vessels.  Smoking marijuana and tobacco and vaping can further damage your lungs.