A health expert is warning a superbug resistant to all antibiotics could already be in New Zealand.

In New Zealand, 48 people have been treated for the CPE bacteria, a bacteria which is becoming resistant to current antibiotics.

Diseases are commonly brought back from overseas countries by people.

However, Auckland University microbiologist Siouxsie Wiles told Kate Hawkesby there have been around 10 cases already where the patient hasn't travelled in recent times.

"If we are starting to see those cases of people who haven't been hospitalised overseas, then I worry that it's already in New Zealand, in healthy people and we are just going to start to see more and more of it as it gets into sick people."

She says widespread antibiotic abuse means it was only a matter of time before this happened.

"These are common bacteria and they are just becoming more and more resistant to antibiotics."

"Essentially we have been using antibiotics really badly...and this particular version of these resistant bacteria has emerged overseas, and now we are just seeing more and more cases of it coming into New Zealand."

Wiles says there has already been a case overseas where a woman died because the bug she was infected with was resistant to the "last resort" antibiotic.

The strains found in New Zealand so far, are still sensitive to antibiotics but she says "it's really only a matter of time until we start seeing bugs that are resistant to everything".

She says there are no symptoms and it is incredibly hard to stop it spreading.

"There isn't really anything anyone can do so it's really more about whether we can protect people who are vulnerable."

LISTEN ABOVE AS SIOUXSIE WILES SPEAKS WITH KATE HAWKSBY