… asked my daughter this morning. I can´t renember having heard any figure before – my rough estimate is about 10,000. It depends very much how you count each viral/bacterial disease and how you are dealing with the ageing process (the recent German invention of IGEL services in medical practice may have doubled disease numbers).
Nevertheless there are only 379 chapters in the renowned Harrisons textbook with the most frequent diseases are about 15. This was the result of a projection already 10 years ago in Nature Medicine. Yea, yea.