Many questions arise from the case of the 40-year-old HIV-positive man charged with wilfully infecting three other men with HIV and attempting to infect a fourth.

Not just why the man, now in custody with name suppression, allegedly did what he did. Or why it took so long for the police to stop him. Or why our laws are so out of date that doctors and other health professionals are uncertain about what to do when they come across such reckless behaviour. Or why HIV is not a notifiable condition.

Puzzling as all that sounds, the greater mystery here is why did the man's sexual partners participate the way they did? Why, after decades of messages honed from the reality of the Aids epidemic 25 years on, did they not practise safe sex?

The slang for engaging is such unprotected sex is "barebacking". As reported on the GayNZ website, there are some - like the man arrested - who have "a strong aversion" to condoms. Some also maintain profiles on international dating websites catering to people specifically seeking unsafe sex.

It's a practice that has Aids Foundation director of HIV prevention and communications Simon Harger-Forde worried: "There is complacency with gay and bisexual men in New Zealand. We would suggest there is a concerning level of non-condom use."

He stresses it's not a trend or that overall the level of condom use isn't dropping, but it is a level of use the Foundation wants to improve.

"From our research and behavioural surveillance and the anecdotes we hear, there are men who are taking pretty huge risks."

Harger-Forde says online dating sites and internet sharing of video pornography are behind what's happening.

"Technology is the perfect tool for the production and reproduction of fantasy and that whole barebacking culture."

The extreme fringe of the subculture has some who deliberately seek to get HIV and spread the infection - involving so-called "bug chasers" and "gift givers".

Why is it happening? Harger-Forde says one of the reasons is possibly due to the success of antiretroviral drugs for treating HIV infections which has changed the perception of HIV from an untreatable terminal illness to a manageable condition. Or it may be a reaction "to being over-messaged and over-health promoted", sometimes referred to as condom fatigue.

Fighting the fantasy and countering these views, says Harger-Forde, is the new challenge facing HIV prevention. One message people need to be reminded about is that HIV is still a highly dangerous and incurable virus. "While it might be manageable, it's not fun to have. It's not something that you want."

The case also highlights shortcomings in our current legislation to deal with reckless or wilful spreading of disease and has renewed calls for the Public Health Bill to be passed.