Slow-spreading outbreak may have hit peak

20:12, Jul 18 2013
whooping cough graphic

A prolonged whooping cough outbreak across the top of the south is expected to drop off at the end of the year despite reported cases in July already exceeding last month's total.

The region had 60 new cases reported by yesterday compared to 50 cases for all of June.

However, Nelson Marlborough medical officer of health Jill Sherwood said outbreaks normally lasted only two years.

Whooping cough
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The existing outbreak was officially declared in August 2011.

"These things tend to have patterns and history says they often last about two years. We expect this will drop off at the end of the year."

Marlborough was a "late starter" in terms of the spread but the numbers had slowly started catching up with Nelson and Tasman, where the outbreak started.


Twelve cases were notified here in June compared to 11 so far this month.

However, there were no cases or only one in some months early on, Dr Sherwood said.

Looking only at Marlborough cases, an outbreak of whooping cough would not have been declared until the end of 2011, she said.

"It had a peak that spring, which was expected, and then kept chugging along."

Better immunisation rates in Marlborough had possibly curbed its spread here. However, the outbreak itself had been prolonged and slow-moving.

"We had a low-level spread and that's why it's taking longer."

Outbreaks of whooping cough normally occurred every four to five years, Dr Sherwood said.

The region's major outbreaks were in 2000 and 2004, with a "little blip" in 2008.

"We thought we were going into one in 2008 but it dropped back down and we went right to 2011, which was seven years from the previous one. That was longer than expected, which was good and perhaps down to better vaccination rates now."

Public health messages associated with the 2009 H1N1 flu pandemic might have helped, she said.

"We wondered if that helped. Not coughing near people and keeping your distance from people [with the disease] really helps to prevent its spread. You can't stop all whooping cough but you can reduce its spread."

Public Health was analysing the current data in the hope of better prevention, she said.

The term "outbreak" is used when there is an increase in cases above what is expected for one region.

In Nelson Marlborough, a whooping cough outbreak is more than three or four cases a month.

The Marlborough Express