How might we know when coronavirus deaths have peaked?
Knowing when the number of new coronavirus-related deaths in the UK has peaked is a key measure in understanding how we are doing in tackling the pandemic.
NHS England publishes figures every day that show the number of deaths in hospitals in England, together with the date on which they occurred.
It is one of the most valuable sources currently available for understanding when coronavirus-related deaths are taking place – even though the figures are only for deaths in hospitals in England where a patient has been tested for Covid-19.
They allow us to analyse changes in the number of deaths based on when the death actually occurred, not when the death was reported.
This gives us a good indicator of the day-to-day growth in the number of deaths – and so provides a clue as to whether growth is accelerating, flattening or even slowing down.
The numbers need to be treated with care, however.
The latest figures, published by NHS England on April 15, are for the period up to 5pm on April 14.
They show that 113 coronavirus-related deaths occurred on April 14, with 399 deaths occurring on April 13 and 540 on April 12.
April 8 has the highest total for a single day: 771.
The reason we need to treat these figures with caution is because they are updated and revised every day, to incorporate deaths that have taken several days or even weeks to be confirmed.
For example, in the figures published by NHS England on April 12, the number of deaths recorded as occurring on April 11 was 121.
This number was then revised upwards to 443 in the bulletin published on April 13, to 575 on April 14, and to 637 in April 15's bulletin.
The number may be revised further in future updates.
In April 15's bulletin, 15 dates have had their totals revised since April 14's bulletin, which gives a sense of just how much of a lag there can be in aggregating the figures.
Reasons for the lag include the time it takes for deaths to be confirmed as testing positive for Covid-19, for post-mortem tests to be processed, and for data from the tests to be validated.
Yet even with these delays, the figures remain one of the most useful sources for analysing the dates of when coronavirus-related deaths are taking place.
The total for April 8 has remained the highest now for several days, despite the daily revisions.
Might this offer a guide to when the peak in hospital deaths in England might have occurred?
Given the scale of some of the daily revisions, combined with the lag in confirming the dates of every death, we will need to wait quite a few more days to be sure.