New Zealand must ramp up the number of workers racing to track down "close contacts" of people who've tested positive to Covid-19 to avert a health system overload, experts say.
It comes as officials today reported another eight confirmed cases, bringing New Zealand's total number to 20.
In an editorial, Otago University's Professor Philip Hill and Associate Professor James Ussher said China may have "exposed an Achilles heel" of the virus through rapid case contact tracing.
Despite an early surge, China had so far recorded just 3,500 deaths in a population of 1.4 billion, against some projections that without any intervention the virus would have infected half the population, at a cost of some seven million deaths.
Epidemiologists have also pointed to other Asian nations – namely Hong Kong, Singapore and Taiwan - appear to have brought Covid-19 under control despite large populations, using heavy disease surveillance and quick contact tracing.
Hill and Ussher said the experiences of Hubei, Covid-19's ground-zero in China, and Italy, which has so far recorded more than 31,500 cases and 2,500 deaths, showed that not acting quickly and limiting activities to just diagnosing and managing cases was "potentially disastrous".
Overseas data had also shown that even large outbreaks – such as that in South Korea, with around 8,320 cases but just over 80 deaths – could be wrestled under control.
"Thirdly, when we look at the various different measures employed by Asian countries who have been successful, there is one common intervention that stands out - it is called rapid case contact management," they said.
"This is simply rapid early diagnosis of as many cases as possible and rapid early isolation of all their contacts. It doesn't even need to be 100 per cent perfect."
They pointed to growing evidence showing that, unlike the Sars coronavirus that emerged in the early 2000s, Covid-19's peak transmissibility happened very early after development of symptoms.
That meant that a strategy limited to just diagnosing cases left the spread too late to stop.
It was also becoming clear that the virus wasn't as efficient a pathogen as influenza in terms of time to causing disease; it took an average five to six days to start causing symptoms.
"This means that there is a bigger window of opportunity to find all the contacts of the case and isolate them."
They said New Zealand had some of the world's best public health practitioners, who carried out case contact management of infectious diseases regularly.
"What is required, apart from increasing capacity and sensitivity to diagnose Covid-19, is an urgent large expansion of our case contact management workforce."
There were different ways to bolster this workforce – such as training people, possibly nursing and medical students, in as little as one to two days.
"We have the opportunity to activate such a plan now before our current workforce becomes overwhelmed."
An emergency $500m cash injection for the health system announced this week included funds to double resources for public health units, specifically to boost capacity for contact tracing.
Contact-tracing could be a painstaking task. In New Zealand's earliest cases, two dozen people had to be tracked down.
One of the three cases confirmed yesterday led to the closure of Dunedin's Logan Park High School, and 150 people having to self-isolate – all of whom would have to be tested.
Ministry of Health director-general of health Dr Ashley Bloomfield said passengers who had been within two seats of those new cases who had recently returned home would also be traced.
"We want to find cases. If we find them, we can put in place appropriate isolation, contact tracing, and community spread. That is the game we are in."
It came as the Government announced today that routine testing for Covid-19 testing across the country would be rolled out to provide more clues about whether there is community transmission.
It would become part of the normal routine for testing for the common flu, and came amid uncertainty about whether Covid-19 is being transmitted in the community.
The Government has defended the number of tests conducted so far, saying the capacity is there and it is up to the clinical experts to decide who to test, taking into account symptoms, travel history and close contact with people suspected of having Covid-19.
But only about 500 tests had been done until this week - though another 500 tests were done yesterday.
• Most cases of Covid-19 in New Zealand have come from overseas. Once a case has been identified, the Ministry of Health and district health boards track down people who may have been exposed to the virus through a process called contact tracing.
• Health services use contact tracing to find people who may have been exposed to an infectious disease. There are two types of contacts – close contacts and casual contacts. Health services give advice to both of these contact types on what they need to do.
• A close contact is anyone who has been close to someone with Covid-19. This can mean living in the same house or spending more than 15 minutes close to someone with Covid-19 such as on a flight, bus or train, or in your workplace.
• A casual contact is someone who has had contact with a case but doesn't meet the criteria for a close contact. This could mean someone travelling on the same aeroplane who was seated away from the case. For example, they were only close to the person with Covid-19 for less than 15 minutes, or were at the same place but not near them.