Dr Peter Saxton is the inaugural New Zealand AIDS Foundation Fellow at the School of Population Health, University of Auckland.

The world's most dangerous infectious disease epidemic of the modern era is reviving, but are we prepared in New Zealand?

The trends are disturbing. Last year New Zealand recorded the highest number of annual HIV diagnoses ever - the fourth increase in a row. Many of these are recent infections.

This World Aids Day, more individuals are living with HIV in New Zealand than ever before.

Experience tells us that HIV evades control when we let down our guard. This virus has killed 40 million people worldwide. Two and a half million people contracted HIV in 2015.

Advertisement

Media hype aside, three decades later we still have no vaccine and no cure.

Treatment for HIV is effective but expenditure on anti-retrovirals is soaring, doubling in the last six years from $16.8 million in 2011 to $32.8 million in 2016. It's estimated that one person diagnosed with HIV at age 20 in New Zealand could cost Pharmac more than $800,000 in anti-HIV treatments over their lifetime.

Given these statistics it's hard to argue that we have the upper hand.

That's why experts agree that prevention makes so much sense, scientifically, morally and fiscally.

We know prevention works. It should be accessible to those who need it most. And for every new infection averted, we can redirect the savings towards other pressing health issues. Investing in HIV has a broad payoff.

Our escalating epidemic is inexcusable and it risks squandering our proud historical record.

When New Zealand saw the first cases more than 30 years ago, the country responded boldly.

Interventions were based on evidence and we agreed on rational policies, bi-partisan political engagement and urgency.

Moralism was rejected in favour of science and co-operation.

The result was an international success story. New Zealand was one of the first countries in the world to report a decline in Aids, and we had one of the lowest rates of HIV diagnoses in gay and bisexual men internationally.

These days, life-saving treatments now mean that people living with HIV can expect a near-normal lifespan if diagnosed early, but effective treatments can also diminish HIV's visibility and reduce support for public health efforts at all levels of society and government.

Meanwhile, internet dating is connecting potential sexual partners like never before and there are concerns that drug-use, particularly methamphetamine, is facilitating HIV transmission through unprotected sex.

Add stigma to the mix and HIV has become a silent and growing epidemic.

To make matters worse, New Zealand has a disintegrating HIV and sexual health workforce badly in need of re-investment.

Despite this, a return to a partnership approach could see New Zealand virtually eliminate HIV transmission within 15 years.

This would require continued safe sex promotion, more frequent HIV testing, and adding two new tools to the mix.

The first tool is making HIV treatment immediately available for people who test HIV positive.

This improves long-term health, but it also makes someone living with HIV almost uninfectious.

The second tool is offering the same HIV treatments as daily pre-exposure prophylaxis (PrEP) to the small number of uninfected individuals at very high risk of contracting HIV.

Studies have shown that PrEP reduces the risk of acquiring HIV by 86-92 per cent.

The World Health Organisation has recommended immediate implementation of both HIV treatment and PrEP, but New Zealand still lags behind.

We urgently need re-engagement and action on HIV. We need to address the inequities that result in 80 per cent of HIV transmission occurring among gay and bisexual men.

We need to evolve and modernise our own responses just as HIV has evolved from a frightening disease in the 1980s to a silent, expanding and expensive epidemic today.