RIVM and NICE provide new figures up to April 18. My earlier discussion of 14 days ago used data from April 2. The Dutch death toll has risen from 1339 to 3601: with one unspecified age, so I will use 3600.
The London Imperial College infection fatality factor (IFF) (they call it a rate) is still not useful for Holland, and the Canary in the Mine principle for the 70-79 age group still gives results that seem reliable – see the former weblog entry for the explanation. The excel sheet has been updated here. (Update June 1 2020: Indeed IFF instead of IFR. Took not only the IFF of 70-79 but also 80+ equal to the LIC values. Took the quarantine hospitalisation ratios as observed, see the text.)
Comparison of the main tables for now and 14 days ago gives these results:
- The 80+ group has become much more unreliable in the Dutch data. Apparently GP doctors and families have a greater tendency not to send such patients to the hospital anymore, given the emotional and physical burden (no contact, low survival rate). This group has 12% more deaths than hospitalised cases, which means that testing is now done more often outside of hospitals. (Indeed, at the end of May, it appears that CBS has registered many “surplus deaths” outside of hospitals.) However, the 70-79 group still seems to opt for the hospital. (This also means that statisticians must check that their time series for the D / H ratio maintain the same definition. It is important to check the performance of hospitals.)
- If the canary works okay, then the (cumulative) prevalence of infections has risen from 92391 (0.5%) to 248160 (1.4%). Officially reported infections were only 16% and are now only 13% of all infections.
- The implied “registered” infection fatality factor (IFF) is about the same: was 1.4% and is 1.45%. (Some call the factor a rate.)
- Deaths are still much underreported however. Deaths outside of hospitals are still hardly tested. The CBS mortality data indicate, as RIVM reported, that there might be another 2000 untested deaths. That is, the “surplus deaths” compared to other years are twice as high as the officially reported deaths attributed to Covid-19.
- It is tempting to infer that the true IFF might also be 3% but this neglects the profile of infections, since people are not infected now randomly, but there are reports that the virus is spreading more rapidly in home-care for the elderly. The officially reported number of cases in the ICUs and the number of deaths is flattening, but if GP doctors and families have decided to avoid hospitalisation, then there might be no real flattening.
- Thus, there still is no true indication that the reproductive number is below 1, though the national lockdown is of such quality that we may expect that it is, at least for the people outside of home-care for elderly. However, the economic cost of this lockdown is huge. There is something very bizarre about the official policy of locking down the country to save people but also allow that the virus spreads in home-care for the elderly who are precisely the most vulnerable.
- While there were 0 deaths below age 50 at the beginning of April, there are now 23 such deaths. This still indicates that the virus works as its own vaccine for this group if we exclude comorbidity.
These new data only affect the left hand side (LHS) of the table. They do not change the fundamental insight on the right hand side (RHS) that the virus works as its own vaccine for the younger group without comorbidity. This means that the suggestion from the former weblog entry for an exit strategy with quarantine zones still stands. If we want to start with this on May 1 then only 11 days are left for planning, i.e. at all levels of government, agencies, companies and families.
Update April 21 and June 1: The table with the exit scenario did not yet contain the implied IFF’s. These have been included now, no longer using the factors from the Imperial Collega but those mentioned in the “canary section”, of which 70+ still is taken from the Imperial College. Of the implied deaths, only 75% applies for the younger group because of herd immunity, and only 4% applies for the elderly because of quarantine. I now assume that the overflow of infections from the exposed population of 12.4 million to the vulnerable group of 5 million will be 4% of the latter, with 25% of development of disease, so that still 1% is in the danger zone. The vulnerable above have an IFF of 4.8% and below an IFF of 5.1%. The less vulnerable above have an IFF of 0.06% and below an IFF of 0.06% too. The overall IFF above does not quite compare to the Quarantine-IFF below, since the weights of the groups have been adjusted (above has population weights and below has deliberate status of infections). Update June 1: The rates of hospitalisation above are 1.55% for the younger and 9.53% for the elderly. These rates have now been used below too. For the non-hospitalised “surplus” deaths, an IFF of 5% has been assumed.