The 20-year-old Canadian, who beat Serena Williams in the final last year, writes that she wants to focus on getting in match shape and returning to games at the highest level.
Her decision means that this year's tournament, which begins in New York on August 31, will be decided without both of last year's winners after Rafael Nadal also threw in the towel for fear of the virus.
ARCHIVE: Andreescu after the US Open title 2019 (August 12, 2019):