According to provincial disease control officer Maria Sabok, the result came from tests done at the Central Public Health laboratory in Port Moresby recently.
Sabok said health workers carried out a mass vaccination on 335 inmates including 154 officers and their families, and reported this case.
The inmate has been vaccinated.
She told TV Wan news that they have enough vaccines to continue the program.
The National Department of Health also reported measles being detected in the Gulf Province.
The suspected cases were detected through heightened surveillance system.
Health secretary Pascoe Kase is now urging the general public not to panic, and for parents to have their children vaccinated.