Two people out of the first 12 tested confidentially at the Dunedin Intravenous Organisation (Divo) - Dunedin’s needle exchange - have been found to have the disease and can now receive drug treatment that cures.
Divo team leader Serena Weatherall said it was "really great" that the test was available and called the disease a "silent epidemic".
"Someone can have no symptoms for up to 30 years or only mild symptoms, for example tiredness."
The disease is contracted through blood-to-blood contact.
While some clear the virus from their system, three in four who contract it go on to have chronic hepatitis C, which can cause liver disease and cancer.
The new test uses a portable machine called GeneXpert.
The portable machine is touring community locations, including needle exchange centres where drug users - a high-risk group - can get tested confidentially.
The machine - funded by a $145,000 government grant - is also being used in a hepatitis C mobile van, touring around Invercargill in August and Dunedin in October.
Another machine, funded by the same grant, would be used further north in the South Island.
The finger pinprick test identifies if someone has an active virus load within an hour.
The killer virus can then be cured with a short course of daily pills, without side effects.
The message of the day is "don’t wait" to get tested and cured. The treatment is effective and easy - but without diagnosis the disease can kill.
New Zealand Needle Exchange Programme South Island executive director Philippa Jones said she was thrilled at the arrival of the GeneXpert test and described it as a "game changer".
"It enables us to give people active virus load test results who don’t normally access care in traditional ways - and get them started on free treatment to be cured of this ... disease.
"You can see the joy and relief on people’s faces when they are rid of hepatitis C.
"It is a silent killer that creeps up on people, who start to feel worse and worse in increments without knowing why. Getting cured can transform their lives."
People most at risk include anyone who has injected drugs, or had medical treatments or tattoos in low- or middle-income countries.
It is estimated 40,000 people have hepatitis C in New Zealand and half of these do not know they have it.
World Hepatitis Day aims to raise global awareness of hepatitis and the importance of testing and ability to get cured. New Zealand is one of 196 countries working towards eliminating hepatitis C as a "public health threat" by 2030.
