Covid 19 coronavirus: the virus was in New Zealand earlier than previously thought

The coronavirus was spreading in New Zealand earlier than previously thought, a study shows that reveals the country’s first known Covid-19 cluster.

New Zealand’s first announced case, a man who had returned to Auckland from Iran via Bali, was reported on February 28, 2020.

But now there is evidence, discovered only through a weak positive test some seven months later, that suggests that another traveler returned from Italy had already started a group of potentially six people.

These cases, hidden at the time, reinforced the urgency the government faced before finally ordering the shutdown a year ago this week.

In the article, published today in the New Zealand Medical Journal, the researchers described an intriguing weak positive test reported to the Waikato Public Health Unit in early September.

It came from a man in his 60s who sought a test while suffering from a sore throat, cough and other symptoms.

However, health officials were unable to identify any potential source of acute Covid-19 infection.

The man had not had any contact with recent confirmed cases, nor had he been near any of the locations involved in the August Auckland group that was active at the time.

However, the patient said he thought he might have been infected months earlier.

On February 23, a family member, along with another close contact of the man, arrived in New Zealand from Lombardy, Italy, one of the worst affected areas at the beginning of the pandemic.

That family member, described as the “index case” of the group, felt ill shortly after arriving home and then sought primary care on February 25 for a “flu-like illness.”

Because the person did not meet the definition of a suspected case at the time for Covid-19, he was ineligible for testing and was instead recommended to isolate himself.

Over the next four days, six other household contacts felt unwell with a similar illness, all of whom isolated themselves until symptoms subsided.

When the “index case” returned to Italy in mid-June, the standard PCR test was negative, but a serological test revealed that the person had produced antibodies to a previous Sars-CoV-2 infection.

Following the man’s weak positive result in September, it was a similar antibody test that indicated that he and five other household contacts had contracted the virus.

Study co-author and Waikato DHB medical health officer Dr. Richard Vipond said the findings suggested the virus was quietly spreading in New Zealand since at least the end of February.

“It would be speculation without any confirmatory laboratory tests, however it seems likely that other cases went undetected in early 2020.”

At that time, the laboratory testing capacity and the case definition as it was, which required travel from China, did not allow for more extensive testing of travelers who had arrived from other countries.

“It wasn’t until later that we learned that there were other countries experiencing significant transmission of Covid-19 in early 2020.”

Vipond and her co-authors, Dr. Elizabeth Becker and Chris Mansell, also noted how the man’s PCR test showed that genetic material could still be detected many months, 201 days in this case, after infection.

Because having viral RNA in a PCR did not always correlate with infectivity, the researchers suggested that serology should be used with repeat PCR to find out the “age” of infections revealed by positive tests.

Ultimately, the curious case backed the government’s call to shut down this week a year ago, Vipond said, along with the benefits of following health advice for flu-like illnesses.

The University of Otago and ESR virologist Dr. Jemma Geohegan also noted how New Zealand was not testing enough during the first few weeks, and that the case definition was “very limited.”

“We probably miss a lot of cases in a similar way,” he said.

“It also shows how prevalent it was in other parts of the world, from very early on.”

Professor Michael Plank, Te Punaha Matatini Covid-19 modeler, said genomic analysis had since told us that about 80 percent of the first cases disappeared without spreading much.

“However, the fact that this group has spread to five household members makes it more likely that this caused ongoing chains of transmission in the community during March 2020,” he said.

“It is quite possible that these transmission chains were only broken after the lockdown began on March 26.

“If we hadn’t locked ourselves in when we did, some of these transmission chains could easily have spawned exponentially growing clusters of their own.”