New Zealand health officials have met to review the latest national and international trends in whooping cough, or pertussis, across the country, which have been closely monitored over recent months and can be particularly dangerous for newborn babies, and older adults, with three babies having died from whooping cough last year, Xinhua news agency reported.

Case numbers consistently increased for several weeks across New Zealand, meeting the threshold for a national epidemic to be declared, a Ministry of Health statement said, citing the country's last major outbreak of pertussis in 2017, which lasted for months and potentially for a year or more.

Whooping cough cases have been steadily increasing again since September, following spikes in May, June and July, according to the Institute of Environmental Science and Research.

There were 263 cases in the past four weeks between October 19 and November 15 in New Zealand, the highest number of cases over a four-week period to date for all of 2024, it said.

New Zealand should also be ready to see similarly high levels of cases over the next 12 months or more, as a number of countries are experiencing record levels of pertussis, possibly due to lower infection rates during the COVID-19 pandemic, said Nicholas Jones, director of public health at the Ministry of Health.

Jones warned of the risk of severe illness among babies either too young to be immunised or whose immunisations are delayed, as well as Maori and Pacific people living in New Zealand who will be most affected.

"Even in countries with very high levels of immunisation, epidemics still occur every few years, but the number of babies who get very sick is much lower when mothers have been vaccinated during pregnancy, and when people are vaccinated on time," she said.