New figures reveal that cases of the potentially deadly disease leptospirosis are two-and-a-half times higher than the four-year average.
The latest public health surveillance report shows that in 2017 there were 142 cases of leptospirosis, well up from an average of 60.
Leptospirosis can feel like a bad case of the flu, but can also progress to rashes, kidney and liver failure, and sometimes death.
The disease is typically seen in farmers and meat workers because it can be picked up through cow urine.
However, public health scholar Jackie Benschop said it's creeping into urban areas and experts think this is likely due to contaminated floodwater.
Ms Benschop said 2017 was a particularly bad year for leptospirosis.
"Last year we heard from veterinarians and animal health labs - they were seeing more cases ... outbreaks in dogs, more outbreaks in sheep, we had an outbreak in alpacas, more cases in horses," she said.
"If there's more animals infected that's more leptospira going from animal urine into the environment."
Ms Benschop is the co-director of Massey University's Molecular Epidemiology and Public Health Laboratory, and has been studying the disease for many years, working with veterinarians, doctors, and communities.
She said the latest figures are interim, and only show the age and gender or the cases, not the occupation or strain of leptospirosis.
This makes it hard to figure out what occupation or strain could be responsible for the huge spike.
Ms Benschop is in Hawke's Bay this week, talking to the District Health Board and primary industries most at risk.
"Particularly young Māori meat workers are carrying the burden of this disease in Hawke's Bay ... it's about giving the same key messages, but also thinking about targeted messaging to address this group."
Because leptospirosis has flu-like symptoms, it can be hard for doctors to diagnose quickly unless they're keeping an eye out.
"It may be getting a wee bit harder to recognise than it was before.
"There's a two-and-a-half times increase in the number of cases ... and as we've talked about before there are more in women and more in occupations that aren't traditionally at risk."