Think of the number of different parasites (species of bacteria, viruses, fungi, flatworm, apicomplexan, etc. that can attack humans. is it reasonable to expect that every other organism faces a similar array of parasites?

It is quite impossible to give the number of the different species enumerated above because they are very minute and can occur whether they are less or not. It is not very reasonable for the conclusion. This is because it would depend upon the surrounding to where an individual is exposed.

Viruses are different from all other infectious microorganisms because they are the only group of microorganisms that cannot replicate outside of a host cell ... Fungi are eukaryotes, meaning that like parasites, their cells have a true nucleus and complex internal structures