PANDEMIC CALCULATIONS: James Cook University epidemiologist Michael Meehan and Professor of Infectious Diseases Modelling and Epidemiology Emma McBryde have co-authored a paper strategies to limit the spread of the COVID-19 pandemic.
PANDEMIC CALCULATIONS: James Cook University epidemiologist Michael Meehan and Professor of Infectious Diseases Modelling and Epidemiology Emma McBryde have co-authored a paper strategies to limit the spread of the COVID-19 pandemic.

Scientists: Don’t flatten the COVID-19 curve, ‘squash it’

WE SHOULD not just flatten the curve of COVID-19 infections, we should "squash it" according to North Queensland epidemiologists.

On the eve of the Federal Government releasing the scientific modelling which has guided decision making during the pandemic, JCU based epidemiologist Michael Meehan has co-authored a scientific paper showing modelling indicates Australia is on the right track towards limiting the spread of the virus (flattening the curve) with its harsh social distancing rules.

Instead of trying to flatten the curve, Dr Meehan was advocating for Australia to "squash the curve" by acting sooner and more effectively, like South Korea and China that used differing approaches to successfully limit the spread of the virus and the number of new infections.

The paper, which was also written by JCU Professor of Infectious Diseases Modelling and Epidemiology Emma McBryde and Monash's James Trauer, highlighted South Korea's approach, conducting a high numbers of tests (around 40 tests for every confirmed case), and China's Hubei province which implemented travel restrictions and universal social distancing with home lockdowns.

PANDEMIC CALCULATIONS: James Cook University epidemiologist Michael Meehan and Professor of Infectious Diseases Modelling and Epidemiology Emma McBryde crunch the numbers to help our government decide where to from here with the COVID-19 pandemic.
PANDEMIC CALCULATIONS: James Cook University epidemiologist Michael Meehan and Professor of Infectious Diseases Modelling and Epidemiology Emma McBryde crunch the numbers to help our government decide where to from here with the COVID-19 pandemic.

"Squashing only requires that we get the average number of new infections per current infectious person below one," Dr Meehan said.

"Early signs indicate that this may already be being achieved with existing restrictions put in place by the Australian Government - however it is still too early to tell for certain.

"What is required from here is a more accurate estimate of this growth rate and how it has reduced following each escalation of the government's intervention policies.

"This will help inform the level of restrictions required to get below the magic number of one new infectious case per infectious person."

Dr Meehan said the pandemic's growth rate over the next two weeks would prove critical in deciding whether the existing control measures and restrictions were working or if an escalation was required which could include ordering lockdowns.

"Until a clearer picture of the growth rate emerges, particularly in response to social distancing and other measures it is probably much better to be safe than sorry," he said.

"Remember, (almost) all settings began with low numbers of cases, so if restrictions are relaxed completely we should expect similar epidemic growth as experienced elsewhere.

"Moreover, we should keep in mind that there may be some infected individuals in the community that have not presented as notified cases because they do not display symptoms."

Once we have the upper hand, Dr Meehan said it would be up to the government to consider how to work its way out of the current lockdown, which was not sustainable in the long term.

"The first consideration is whether to let schools go back. Young adults and children are at very low risk of severe disease and probably less infectious too," he said.

INTERMITTENT STRATEGY: By loosening and tightening restrictions, the number of cases requiring hospitalisation (red), and requiring ICU admission (maroon) can be controlled while the population develops herd immunity.
INTERMITTENT STRATEGY: By loosening and tightening restrictions, the number of cases requiring hospitalisation (red), and requiring ICU admission (maroon) can be controlled while the population develops herd immunity.

With Australia's approach towards flattening the curve, Dr Meehan said the big issue was it required a delicate balance to ensure we just skate under the maximum hospital capacity curve while still allowing a sufficient proportion of the population to get infected to avoid future epidemic waves.

He said this could be very difficult and could go horribly wrong if the effectiveness of interventions are over-estimated.

"The other thing to keep in mind is that even if we are able to stay within the hospital capacity, if millions of people get infected many people will still die," Dr Meehan said.

"In the 'squash' scenario we attempt to keep the case numbers much lower at any single point in time (and hopefully throughout the course of the epidemic) until another solution arises, e.g., a vaccine."

Herd immunity requires about 60 per cent or more of Australians to be infected with the virus, in order to stop it circulating in the community.

APPROACHES COMPARED: By having no restrictions on the population, millions would catch COVID-19, many would die and eventually there would be herd immunity in the population. Other exposure limiting approaches wouldn't create full herd immunity.
APPROACHES COMPARED: By having no restrictions on the population, millions would catch COVID-19, many would die and eventually there would be herd immunity in the population. Other exposure limiting approaches wouldn't create full herd immunity.

Epidemiologists say the COVID-19 pandemic will only end when enough people have been infected to achieve herd immunity or scientists develop a vaccine, which experts estimate to be least 12 to 18 months away.

We also have to prepare for the possibility that a vaccine can not be developed.

If Australia is successful in suppressing and overcoming the first epidemic wave with the "squash" strategy, the population would still be susceptible to the virus and would need to sustain the protective measures otherwise the epidemic would re-establish itself.

Dr Meehan's paper speculates what approaches might be taken to build up herd immunity.

"Fundamentally, there are only three possibilities: 1) relax restrictions and allow an epidemic with similar characteristics to the first wave, 2) maintain suppression until vaccination is possible (or indefinitely), and 3) allow limited circulation to occur while protecting the vulnerable," the paper said.

Calculation of expected infection fatality rate in Australia, based on Australian age distributionand age-specific estimated infection fatality rate in Wuhan Province, China.
Calculation of expected infection fatality rate in Australia, based on Australian age distributionand age-specific estimated infection fatality rate in Wuhan Province, China.

The lockdown would never end for high-risk groups that would need to remain cloistered in their homes until a vaccine was developed or herd immunity established.

Dr Meehan feared for the health of people in Australia's remote communities, like CQ's Woorabinda Aboriginal community, who were a "particularly vulnerable group" who had made the decision to reduce visitors to essential services only.

"However, they will also need to practice self-quarantine within the communities. They have to anticipate that they may still get cases, and have to ensure that they do not transmit them further around the community," he said.

To read Dr Meehan's co-authored paper, it publicly available online at: www.medrxiv.org/content/10.1101/2020.03.30.20048009v1



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