KEY POINTS:
A national outbreak of a "potent" and rare type of salmonella has health officials puzzled.
Since mid-October, 36 cases of salmonella typhimurium phage type 42 have been reported nationwide, compared with 15 cases for the whole of last year and 28 in 2006.
Environmental Science and Research started a national investigation about a week ago, with public health units and the Food Safety Authority trying to identify the source of the bacteria.
It is likely to be some form of food product.
Ministry of Health chief adviser of population, Greg Simmons, told The Press the outbreak was a "significant" one.
There have been 16 confirmed cases of type 42 in Christchurch, nine in Dunedin, five in Nelson, two in Auckland and one each in Greymouth, Rotorua, Whakatane and Waikato.
At least five people needed hospital treatment.
Mr Simmons said babies, the elderly and those with compromised immune systems could become severely dehydrated if they picked up the bug.
- NZPA
