Definition: Morbific is an adjective meaning "causing disease".
Pronunciation: More beh fick
Origin: From Latin morbus - sick
Why use it? There really isn't another word with the same meaning as morbific. Pathogenic is similar, but implies a pathogen; morbific does not.
Examples. I found a few examples, but I prefer some new ones that are more general, e.g.
Although poverty does not directly cause disease, it is associated with many morbific conditions.
Medical care in earlier days not only rarely cured people, it was often morbific.