An undetectable viral load is when there are less than 20 particles, called "copies", of HIV found in a person's blood.
"That combined with regular sexual health screening and monitoring my viral load is what safe sex looks like in 2017," Tredway told the Herald.
"We have lots of options to protect ourselves and others."
Tredway, who contracted HIV from a partner he was entering a monogamous relationship with, said he was not endorsing sex without condoms, rather people's responsibility to look after themselves and use the tools available to them.
"We live in a time where there are scientifically proven and highly effective options and we need to be having these conversations without the scapegoating and misconceptions."
He said the only reason he entered Mr Gay NZ was to challenge the stigma that people living with HIV face regularly.
"That untrue notion that we are somehow less than the rest of the community. That we are unsafe to be around, or unclean and that we can't live our lives with transparency and dignity."
The online backlash was "difficult to take", but also validated his reasons for entering Mr Gay NZ, he said.
New Zealand Aids Foundation executive director Jason Myers said HIV prevention science had moved rapidly in the past two years and had shown that people with HIV and on treatment could reach an undetectable viral load which rendered them virtually non-infectious.
"And so, while in the good old days condoms are the only way to prevent the onwards transmission of HIV we are now in a space in 2017 where there are a number of tools that are equally as useful."
In addition to condoms, undetectable viral loads and Pre-exposure prophylaxis were also viable options to prevent HIV transmission.
The NZAF says it is legal to have sex without condoms if a person has disclosed their HIV status.
In an open letter, Mr Gay NZ producer Matt Fistonich said the organisation would continue to support Tredway as the 2017 Mr Gay New Zealand winner and his advocacy role for the community and HIV stigma and awareness.
"What Mr Tredway does in the privacy of is own home, is not an issue, and ironically any discussion around Mr Tredway's private life highlights and reinforces how as a community we need to continue to fight HIV-related stigma, and raise awareness of the damaging and hurtful attitudes of a vocal minority that need to change."