Most germs ultimately do not cause a disease, as most germs are harmless and the immune system kills many harmful germs.
The word "ultimately" is an adverb that modifies the phrase most germs.
Germs are found everywhere around us and these includes in water, air, in the soil and even on our bodies. We know that some germs cause various diseases while majority of them are harmless. For example, some microbes or microorganisms known as germs are found in our stomach and they generally help in aiding digestion.
