Covid-free in 21 days?
New Zealand could be declared coronavirus-free in 21 days and with so few known active cases left, may have already eliminated the disease, an epidemic scholar says.
Pinpointing an elimination or ‘‘epidemic extinction’’ date carries potential consequences for New Zealand’s economy, foreign relations, and travel restrictions.
The onset date of the most recent active case’s symptoms was a key factor in knowing when elimination could be achieved, epidemiologist Professor Michael Baker said yesterday. That date differed from the date a person returned positive test results, Baker said.
As of 1pm yesterday, only eight active cases were reported in New Zealand.
Baker, from the University of Otago, said it was very likely New Zealand was close to eliminating Covid-19 and may have done so already. He said New Zealand might have reached the point where the latest active case was infected so long ago that it was not realistic for that person to infect anybody else. He understood the Government already had the data identifying the most recent active case’s onset date.
The Ministry of Health defines anybody whose onset date was 10 days prior as having ‘‘recovered’’.
A study from Taiwan found nobody was infected through contact more than five days after somebody showed symptoms. That study suggested contact tracers start investigations four days before symptoms showed.
Baker and the four other researchers outlined scenarios that could speed up or impede the country’s ability to declare itself free of coronavirus. They said Government transparency on health data, high testing rates and co-operation with Australia would be needed to achieve certainty on elimination.
The Otago study outlined multiple scenarios. At minimum, it would take 27 to 33 days of no new detected cases for the country to reach one definition of epidemic extinction. With no new cases
since May 22, the country could be declared free of the virus by June 18 with 95 per cent probability, according to the study’s definitions. But for a 99 per cent probability of epidemic extinction, the equivalent time period was up to 44 days.
If a new case were to be announced on May 29, and the higher level of certainty desired, ‘‘epidemic extinction’’ might not be declared until July 14.
The Ministry of Health has been approached for comment about onset dates and what definitions it favoured for declaring the country free of coronavirus.
Baker, Professor Nick Wilson, Dr Matthew Parry, Dr Ayesha Verrall, and Professor Martin
Eichner said Taiwan and Iceland were approaching elimination.
And the Otago experts said when New Zealand achieved Covid-19 elimination status, it could potentially phase out nearly all restrictive disease control measures.
They said quarantine-free travel might start with other Covid-free island jurisdictions for which New Zealand was the major or sole air-traffic transit hub. Such countries included Samoa, Tonga, Niue, and the Cook Islands.
Taiwan could also be a candidate, the Otago scholars said.
High levels of testing for people with coughs, fever, and respiratory ailments would be needed, the researchers added.