How does Cryptosporidium spread from one host to another?

Cryptosporidium is a protozoan parasite that infects the gut of humans and other mammals. Unlike many other parasitic protozoans that require multiple hosts or insect vectors to complete their life cycles, Cryptosporidium has a one-host life cycle.12

The parasite spreads from one host to another through a resistant cyst stage known as an oocyst. These oocysts are shed by an infected host and can then be ingested by a new host, where the parasite proceeds to live inside the cells lining the intestines or, less commonly, the lungs. Once inside the new host, the parasite completes its asexual reproductive stages.2