Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Q: Sentence1: Protozoa make humans sick when they become human parasites. 
Sentence2: paramecium are single celled animals that make humans sick when they become human parasites.

A: become
****
Q: Sentence1: disease-causing microbes have a negative impact on the body. 
Sentence2: pathogens have a negative impact on the body.

A: body
****
Q: Sentence1: HIV infects and destroys helper T cells. 
Sentence2: Lets Meet the HIV HIV is a new virus.

A:
HIV
****