What type of organism causes malaria?

Malaria is caused by protozoan parasites belonging to the genus Plasmodium. These microorganisms are single-celled eukaryotic organisms and are responsible for the disease's transmission through the bite of infected female Anopheles mosquitoes. Once introduced into the host's bloodstream, the protozoa invade red blood cells, multiply, and lead to the symptoms associated with malaria, such as fever, chills, and anemia.

The other types of organisms listed—bacteria, viruses, and fungi—are distinct in their structure and mode of action. Bacteria are prokaryotic organisms, viruses are acellular and require a host to replicate, while fungi are primarily eukaryotic organisms that can cause various infections but do not cause malaria. Therefore, the only organism responsible for malaria in this context is a protozoan.