Contact tracing of Covid-19 bolstered

The Director-General of Health says tracing contacts of confirmed Covid-19 cases is incredibly important. David Williams reports.

With the country going into lockdown, contact tracing has just become a whole lot easier. Which is the point.

If the only people you’re mixing with are those in your house – as it will be from Wednesday – then if one of you becomes sick it’s going to be easy to isolate and test your close contacts, to slow the spread of the virus.

As Otago University Department of Public Health's Professor Michael Baker, an infectious disease epidemiologist, told Newsroom before Prime Minister Jacinda Ardern’s bombshell announcement: “We should be doing a huge amount of social distancing as soon as we can and as fast as we can, if we want to stay in containment.”

Director-General of Health Ashley Bloomfield showed today that health officials were already listening to calls to bolster contact tracing. In his daily briefing, Bloomfield announced a further 36 confirmed Covid-19 cases, taking the total to 102. The increase in cases was expected, he said.

“Our contact tracing efforts are incredibly important and they are being ramped up to support this public health response.”

Asked if he was concerned about a potential backlog of contact tracing, Bloomfield said: “In addition to the capacity there is in all our public health units, we have stood up a team here in the ministry that is able to supplement the public health units. It can manage, at the moment, up to 50 new cases a day, in addition to that public health unit capacity. And it is also scalable up, as and when needed.”

Last week, Otago Medical School’s Professor Philip Hill and University of Otago Associate Professor James Ussher argued the Covid-19 response demanded “an urgent, large expansion of our case contact management workforce”.

Most significant restrictions in modern history

At a press conference at Parliament today, Ardern announced the country would immediately move to alert level three and to level four in 48 hours, meaning the closure of all non-essential businesses, plus schools, universities and daycares. The move was prompted by confirmation of community transmission, in two cases.

The risks of not taking these restrictions were stark, given the experience of the outbreak in some countries.

“If community transmission takes off in New Zealand the number of cases will double every five days,” Ardern said. “If that happens unchecked, our health system will be inundated and tens of thousands of New Zealanders will die.”

Professor Hill is co-director of Otago Medical School’s Centre for International Health, part of the Department of Preventive and Social Medicine. He says it’s very difficult to ascertain the virus’s spread right now given its current trajectory predominantly reflects the rate of disease in travellers.

How widespread could it be? Hill says testing of 150 students at Logan Park High School resulted in zero positive tests. “However, there clearly is some [community transmission] and we will understand how much more clearly in the next few weeks.”

Where might the country be in four weeks? Hill’s firm response: “No one knows. I would be guessing!”

Lockdown increases chances of containing, stamping out disease

By going to alert level three and then four, University of Auckland Professor Shaun Hendy says the country should be able to significantly reduce person-to-person contacts over the next few weeks and slow the virus’s spread.

“It seems likely that Covid-19 community transmission has been taking place here, with two cases now unable to be linked to overseas travel. This is where we run into the danger of seeing exponential growth that has overwhelmed healthcare systems overseas. By locking the country down now, the Government will give the testing regime and our contact tracing teams a good chance of containing and stamping out the disease.”

With less contact between people there’s less chance of catching the disease, he says, and less chance of those who are infected passing it on. “This will slow the rate it passes through the community, and if we can keep our contact tracing teams going by giving them fewer cases to chase, we will be able to continue to identify people for quarantine and testing.”

The number of confirmed cases will likely rise in the coming weeks, says Hendy, who is the director of Te Pūnaha Matatini, a research centre focused on complex systems and networks.

“A key thing to watch will be the doubling time of cases not linked to overseas travel. We may see that get shorter, but if we are successful it will begin to increase. This is what we have seen in South Korea before the number of cases eventually began to fall.”

That is the point where containment is deemed to be successful and the Government can consider dropping the alert levels – and restricted movement.

Hendy adds: “We may also see alert levels drop in some parts of the country if the Government becomes confident that we are not seeing community transmission there and can restrict travel sufficiently from regions at higher alert levels.”

It’s likely new technology will be deployed in the coming weeks and months.

Bloomfield, the Director-General of Health, said today the Health Ministry has “many, many offers” from overseas for different virus testing options. “We’re looking at all of them.”

He also confirmed he participated in a teleconference yesterday with a group of “senior and well-known private sector people”. This morning he spoke to Trade Me founder Sam Morgan about a WhatsApp-based application for sharing information. “All of these options and offers are being actively explored,” Bloomfield said.

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