Question

add a comma, semicolon, or colon if needed. otherwise, submit the text without any additional punctuation. at the conference, dr. joyce saw several presentations on rare infectious diseases crimean-congo hemorrhagic fever, sleeping sickness, chagas disease, and chikungunya fever.

Explanation:

A colon is used to introduce a list. Here, "rare infectious diseases" is followed by a list of specific diseases, so a colon is needed after "diseases".

Answer:

At the conference, Dr. Joyce saw several presentations on rare infectious diseases: Crimean - Congo hemorrhagic fever, sleeping sickness, Chagas disease, and Chikungunya fever.