The daily announcement of new COVID cases has become part of the rhythm of life for Victorians. It can be an unsettling announcement, especially over the past fortnight as a ‘stubborn tail’ casts doubt over the state’s ability to ease restrictions as soon as hoped.
The headline number attracts a lot of attention, as do the 14-day moving average and the 14-day ‘mystery case’ total, since these are the metrics used in the State Government’s roadmap to a ‘COVID normal’. But they are not the only useful numbers to keep an eye on. When the total caseload is so small, it is also useful to distinguish between cases from a known source, cases which are successfully traced, and cases which remain a mystery. These provide a perspective on contact tracing efforts.
This information is provided in daily media releases and in statements and tweets by the Victorian Chief Health Officer. The chart above presents it in a simple visual form.
The chart makes a few things apparent. First, there have been 10 or fewer cases requiring investigation each day in the past fortnight. Second, most of those investigations have been successful: about 90 per cent of cases have been traced. Third, there is still a small but significant number of mystery cases. These cases indicate gaps in our knowledge about where the virus has spread, and those gaps are riskier the fewer restrictions are in place.
No single metric should be taken as the perfect measure of progress. Monitoring the types of cases, not just the total number, offers a more vivid picture of the trends that will shape the coming weeks and months.