Which parasite type includes worms that can infect humans?

The answer is helminths because this category of parasites specifically includes worm-like organisms that can infect humans. Helminths are multicellular organisms and are divided into different groups, including nematodes (roundworms), trematodes (flatworms), and cestodes (tapeworms). These worms can enter the human body through various routes, including ingestion, skin penetration, or through vectors.

In contrast, protozoa, which are unicellular organisms, can also be parasitic but are different from helminths as they do not include worms. Bacteria and viruses, while pathogens that can cause disease in humans, are not classified as parasites that include worm types. Therefore, helminths is the correct answer as they are the specific type of parasite that encompasses the worms capable of human infection.