18 Mar 2020

Covid-19 spread in NZ: Answering the big questions

5:04 pm on 18 March 2020

New Zealand has 20 cases of the Covid-19 coronavirus. As the health system deals with the pandemic, the Science Media Centre spoke to experts who reveal how patients are treated and likelihood of the disease spreading.

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Photo: AFP

What happens if a person suspected to be infected with Covid-19 is taken to hospital?

Dr Ayesha Verrall who is a senior lecturer at the Department of Pathology and Molecular Medicine at the University of Otago in Wellington says:

"Patients who are thought to have Covid-19 enter hospital into an isolation room with staff wearing masks, gloves and aprons from the beginning.

"Their initial assessment would be focused on working out if it was coronavirus or another infection, and assessing how severe it is.

Verrall said people who had a severe illness or with poorly functioning other organs were struggling to maintain good blood oxygen levels.

"We know Chinese doctors found CT scans were very helpful in working out if people had a viral pneumonia but we're still figuring out if this a feasible part of our routine assessment."

How are coronavirus patients treated?

"The treatment for coronavirus is supportive. That means there isn't a specific antiviral medicine that can use to shorten the illness or reduce its severity," Verrall said.

"The main support people need is with their breathing, either oxygen delivered by a thin tube to their nose, or if that isn't enough their breathing can be supported by a machine that breathes for them called a ventilator. This type of support can only be given in intensive care units by highly specialised staff."

She said so far data suggested people with Covid-19 had longer stays in hospital than for other infections. Mild cases might need a week's stay whereas severe cases could need a couple of weeks or more.

Verrall, who is also the deputy chair of Capital and Coast DHB, said New Zealand and Australian doctors were collaborating on studies with scientists from around the world for treatments including studying existing medicines that were effective on other viruses.

Is our health system ready for the patient demand of a pandemic?

University of Auckland healthcare operations research specialist Dr Michael O'Sullivan said even before the pandemic, various organisations within the NZ health system were striving to deal with their workloads more effectively.

"The pandemic is going to place extra load on health resources with the extra complexity of infection and the need for isolation, not to mention the problem of healthcare providers becoming infected and needing to be isolated/recover," he said.

"Other services, such as elective surgeries, may need to take a back seat to coronavirus treatment in the short/medium-term. I think careful planning and hard work are going to be needed for NZ's health system."

What if everyone took measures to flatten the curve?

"Flattening the curve will definitely help because it means that the demand for coronavirus treatment resources, eg negative pressure rooms, will be spread out over a longer time period," O'Sullivan said.

"This means that utilisation of these resources will be more manageable and it will also enable health practitioners to get time to recuperate and refresh."

What else can the public or the health system do to ease the burden of patients?

"We have been working on models for virtual health organisations, eg hospitals, medical centres etc, that enable these organisations to experiment with various initiatives like dedicated coronavirus services, phone triage etc, and evaluate their effect on both the health system and patient experiences and outcomes," O'Sullivan said.

"There are many trade-offs that may need to be explored before an organisation settles on the best way forward for their staff and patients."

How do you predict the spread of a disease like Covid-19?

"In order to model how the virus might spread once community transmission has started, we need to estimate the generation interval and the basic reproduction number," Massey University mathematical biology professor Mick Roberts said.

"The generation interval (average time from me being infected to me infecting others) is not observable, so it is usually inferred from the serial interval (average time from me developing symptoms to those that I infect developing symptoms). The basic reproduction number is the average number of others that I infect while I am infectious.

"Both of these quantities are difficult to estimate, especially in the early stages of an epidemic, and they differ between communities. But both of these quantities are needed to forecast the rate of spread of infection, and the effectiveness of potential control measures," he said.

"For example, a short generation interval makes contact tracing and isolation less effective, and a low basic reproduction number makes social distancing more effective."

How does this apply to New Zealand?

"There is no evidence of community transmission in New Zealand at the moment. Most international estimates have a basic reproduction number greater than two, and a generation interval of around six days," Roberts said.

An epidemic with these characteristics, without any interventions or behaviour change in the population, would infect around 80 percent of the population, he added.

"This is not going to happen. Interventions have already been announced, and it is important that these are respected.

"Modelling studies are continuing in order to get better estimates, and to determine the likely effect of interventions on reducing the basic reproduction number and increasing the generation interval. Taken together this will reduce the incidence of infection and the burden on the health service."

As Covid-19 spreads around the world, it can be daunting keeping up with the information. For RNZ, our responsibility is to give you verified, up to the minute, trustworthy information to help you make decisions about your lives and your health. We'll also be asking questions of officials and decision makers about how they're responding to the virus. Our aim is to keep you informed.

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