A health board in New Zealand has been hit by a cyber security incident which has affected five hospitals.

Waikato District Health Board confirmed on 18 May that it was addressing “a cyber security incident” and was “experiencing a full outage” of its information systems.

The district board said the incident has affected five hospitals (Waikato, Thames, Tokoroa, Te Kuiti and Taumarunui) “to varying degrees”.

An update, posted on May 19, said “good progress” had been made overnight to get systems back online.

“Our staff are working to restore the infected systems and on the remediation process. We are working with the relevant government departments to ensure a secure environment is successfully re-established,” the statement said.

“However, this is a complex process which will take more time to resolve. We currently have business continuity plans in place to keep our services running into the weekend.

“We are currently working with other government departments to investigate the cause, but are working on the theory that the initial incursion was via an email attachment. A forensic investigation is ongoing.”

The statement also revealed that as a result of the disruption on 18 May six elective surgeries were cancelled, while 95 went ahead.

The incident follows a large-scale cyber attack on health IT systems in the Republic of Ireland on 14 May. Services have been switched off following reports of a possible “human-operated ‘Conti’ ransomware attack that had severely disabled a number of systems”.