The source of the outbreak has baffled health officials, who said they were confident there were no local transmission of the virus in New Zealand for 102 days and that the family had not travelled overseas.

“We are working hard to put together pieces of the puzzle on how this family got infected,” said Director General of Health Ashley Bloomfield.

Investigations were zeroing in on the potential the virus was imported by freight. Bloomfield said surface testing was underway at an Auckland cool store where a man from the infected family worked.

“We know the virus can survive within refrigerated environments for quite some time,” Bloomfield said during a televised media conference.