‘Nowcasting’: New Modelling Shows Australian Cases Declining, but We Can’t Relax Yet

This blog is part of a series relating to the economic and social impacts of the COVID-19, novel coronavirus outbreak of 2020. 

Nowcasting, a portmanteau of “now” and “forecasting”, is a method of very short-range forecasting that uses recent data to determine the present and near future and, in some disciplines, the very recent past. It is frequently used in meteorology and economics and also proves beneficial in predicting public health circumstances, particularly during times of crisis such as the coronavirus pandemic.  Recently, the Doherty Institute, a joint initiative from the University of Melbourne and The Royal Melbourne Hospital, teamed up with a team of international experts to analyse Australian coronavirus data from the past 14 days to infer the current state of the pandemic and what we can expect in the coming weeks.

The nowcasting modelling shows that, within Australia, the number of new cases being discovered as well as the total number of cumulative cases are decreasing.  The basic reproduction number (or Reff) in Australia is 0.72, meaning each person who contracts coronavirus will, on average, transmit it to less than one other person.  As the general Reff for coronavirus is estimated to be about 2.5, this indicates that current containment measures are effective.  Furthermore, the nowcasting modelling suggests that about 92% of coronavirus cases in Australia are being detected, with each state and territory detecting over 80% of cases.  

It is important to note that this current modelling uses actual Australian data, as opposed to the modelling released a few weeks ago that was purely theoretical and relied on international data.  Chief Medical Officer Brendan Murphy noted that, because the number of coronavirus cases in Australia is declining, the modelling will become less accurate in future weeks as fewer cases means less data to input.  While the current modelling does predict a decline in numbers over the coming weeks, Mr Murphy “cautioned against taking that as a reason to be complacent”.

The nowcast modelling indicates that social distancing and other measures have been effective in containing the spread of coronavirus.  This does not mean, however, that these restrictions should be relaxed.  In order to keep Reff below 1 and reduce the likelihood of community transmission, we must not take the nowcasting data as an invitation to return to a pre-coronavirus way of life.  Removing restrictions now would likely cause a resurgence of coronavirus, risking the lives and well-being of millions and sending us, as a country, back to square one. This is not outside the realm of possibility. For example, Singapore had initially been hailed for their exemplary national response to coronavirus before experiencing a second wave that saw a massive spike of cases. They are now experiencing some of the highest numbers of new cases in Asia, driven largely by the spread of the virus among migrant workers dwelling in crowded dormitories. This is all to say that there are blind spots in a country’s response that may only be clear once they have attempted to relax measures. There are cautionary tales of regions that relaxed their measures too soon, putting the economy above health, and saw huge increases in the case numbers as a result. This was the case Hokkaido, who declared a national emergency after the second wave hit the region. 

As we continue to navigate this pandemic, there are clear sacrifices being made at all levels of our lives. Having access to real-time modelling is a vital component to being able to make the most informed decisions possible as we balance the risks and rewards of different strategies moving forward. What other kinds of information will we need to model the potential impacts of different scenarios? And how will this information be used to balance the economic and health needs of Australians?

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