Actually there are entire sects of Christianity with millions of followers that believe diseases are not caused by germs, at least not in any sense that would indicate prevention or treatement based on germ theory.
Where are the "entire sects" of Christianity that believe that diseases are not caused by germs? As far as that goes, there are atheists who believe in mass murder to promote social justice, called Communists, and there were pagans who believed in mass murder in order to purify the Aryan race, called Nazis. Would you imply that atheists and pagans advocate genocide?