The phrase "documented cases" refers to situations or incidents that have been recorded or written down in an official or reliable manner. Full definition
If so, it would be the first documented case of sexual transmission of an insect - borne disease. (sciencemag.org)
After any hospitalized patient is examined, a room is seen, or surgical procedure performed, the doctors and technicians must thoroughly document the case in the record. (emeraldcityanimalhospital.com)
«There aren't many documented cases of urban evolution yet, but people are going to start looking for them in earnest,» he says. (newscientist.com)