Chimpanzees have cleaner beds than humans, study says

Chimpanzees maintain cleaner sleeping environments than humans by building new nests each night, resulting in lower bacteria levels. A study by North Carolina State University found that only 3.5% of bacteria in chimpanzee nests originated from their own bodies, compared to 35% in human beds. This difference is attributed to the chimpanzees' habit of changing their sleeping area daily, unlike humans who typically sleep in the same bed repeatedly.

What did the previous North Carolina study find about the bacteria levels in human beds?

What is one explanation for the differences in bacteria levels between chimpanzee nests and human beds?