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.

The World Health Organization and Russian health authorities are discussing the process for possible WHO prequalification, a WHO spokesman said on Tuesday.

“Prequalification of any vaccine includes the rigorous review and assessment of all required safety and efficacy data,” WHO spokesman Tarik Jasarevic told a U.N. briefing in Geneva, referring to clinical trials.

Experts say that while the SARS-CoV-2 virus is capable of infiltrating food or food packaging materials, it cannot reproduce and cannot survive at room temperature for long.

However, Li Fengqin, who heads a microbiology lab at the China National Center for Food Safety Risk Assessment told reporters in June that contaminated food put in cold storage could be a potential source of transmission.