Question

fix any words that are used incorrectly. if there are no errors, submit the text without making any changes. their arent many treatments currently available for viral infections, but one experimental new drug looks promising. this drug kills human cells infected with anyone of a number of different viruses.

Explanation:

• "Their" is a possessive pronoun. The correct form here should be "There" (as in "There aren't...", which is the correct structure for indicating existence).
• "Anyone" is used for people. The correct word for referring to things (in this case, viruses) is "any".

Answer:

There aren't many treatments currently available for viral infections, but one experimental new drug looks promising. This drug kills human cells infected with any of a number of different viruses.