A failure to properly sterilise surgical equipment at Hawke's Bay Hospital was caused by "many errors", an external review has found.
One of those errors was the reliance on a printer that hadn't been working for months, the review, released today, found.
On the evening of February 1, there were three main factors that contributed to the event occurring.
Most significantly, it found the printer on the autoclave had not been working for some months.
Earlier this year, it was found a batch of 91 pieces of equipment at Hawke's Bay Hospital were properly cleaned, heated to a high temperature and dried, but failed to go through the final sterilisation process overnight between February 1 and 2.
Fifty-five patients from across Hawke's Bay underwent HIV and hepatitis tests because the inadequately sterilised surgical equipment may have been used on them.
Three children under the age of 16 and four people over the age of 70 were included in the group.
Of those affected, 18 people were operated on in the main theatre block of Hawke's Bay Hospital.
The remaining packs were also sent to oral health and gynaecological clinics throughout Hawke's Bay, where they were then used by district nurses.