An outbreak of whooping cough in Otago children has spread to Dunedin.
Public Health South Medical Officer of Health Marion Poore said GPs had notified 125 cases of likely whooping cough in the past two weeks, with laboratory tests confirming 24.
The number has risen from 80 cases a week ago.
The bacterial infection, also called pertussis, was first identified in the Wanaka area, but cases were now showing up in Cromwell, Queenstown and Dunedin.
"We're now seeing cases from around the district. It's clear that there's background illness going on but this would certainly be an increase in the number of cases and therefore an outbreak by this definition."
Ms Poore said no one had been admitted to hospital but the infection could be serious.