The lower North and South Islands are the biggest hotspots for whooping cough as an epidemic sweeps the country, official data shows. Health officials on Friday declared a whooping cough epidemic and put a nationally coordinated response in place.

Caused by the bacteria Bordetella pertussis, the highly contagious illness - known as whooping cough for the whoop sounding intake of breath that can follow coughing fits, or as the 100-day cough, for the lingering cough that can take weeks or months to resolve, causes breathing difficulties and severe coughing fits.

Health officials in Ohio are sounding the alarm as cases of whooping cough, also known as pertussis, are on the rise.