Given a scientific question, generate a correct answer to it.

Input: Consider Input: Name the fever that is caused by a virus that has antigens similar to molecules in human heart tissues.

Output: rheumatic fever

Input: Consider Input: What are long chains of amino acids?

Output: proteins

Input: Consider Input: Any sound with a frequency above the highest audible frequency is defined as what, a phenomenon useful in medical diagnosis and therapy?
Output: ultrasound