One in five HIV-positive men who have sex with men (MSM) is unaware of his status, according to a study by Melbourne’s Burnet Institute of HIV and STI Research as reported by the Australian Broadcasting Corporation.

According to the article, researchers surveyed 745 MSM at gay venues in Melbourne, asking them about their HIV status and risk behaviors. Saliva samples were also collected to check against the self-reported results.

Roughly 10 percent of participants were found to be HIV positive.

“That allowed us firstly to more reliably estimate HIV prevalence in the gay community, which we don’t really have a good handle on because previous estimates have been based on self-report,” said Mark Stoove, MD. “It gave us a mechanism where we could estimate how many people had an unrecognized infection.”