Waikato Hospital has closed some of its wards to new admissions after four patients tested positive for a drug-resistant superbug.
Carbapenem-resistant enterobacteriaceae (CRE) is resistant to multiple drugs.
The hospital's infectious disease physician and infection control committee chair, Dr Erana Gray, said controls had been put on its older persons and rehabilitation wards.
She said the organism had proven difficult to manage overseas, but remained uncommon in New Zealand.
Dr Gray said tests were being conducted in the Older Persons and Rehabilitation ward.
"I think of the fifty or so samples that we've sent already, none of those are positive, so that's a really good sign that even though it has transferred to three other people from that one initial one, that a lot of other screening has come back negative so far."
Dr Gray said most people who caught the bug did not become unwell, as it lived harmlessly in the gut, but it was more likely to cause a problem in people who were already sick.
