I’m seeing lots of different numbers thrown about, and I’m not quite sure where all of those come from. Here are the numbers as given by the Danish Corona strategy plan, published/updated March 10.
Typical infection rate in a epidemic (first wave): 5-10%
Typical infection rate in a pandemic (first wave): 10-30%
These are numbers based on past similar epidemics/pandemics. The actual infection rate will depend a lot on the measures put in place to contain and mitigate spread. The goal of the SST is to limit the infection rate to 10% in the first wave (while obviously working with worst-case scenarios where the infection rate is higher). They are planning for multiple waves of infection into at least 2021 (best case scenario: future waves turn out to be limited, due to health services/nations now being prepared tp handle Covid-19 and/or a vaccine is developed).
Number of infected who will need to contact the health services: 10%
That is, 90% will have so mild symptoms that they won’t contact the doctor or will be told to stay home (and thus won’t get a diagnosis). The SST number seems primarily based on typical epidemic numbers from flu. Possibly iffy, but there are no numbers on which we can base a precise estimate. The number is probably somewhere between 5-20% (early estimates were that only 5% of all cases were being identified, with 95% flying under the radar due to mild symptoms; the highest estimates I’ve seen is 20%).
Number of diagnosed cases requiring hospitalization: 20%
Number of hospitalized cases requiring intensive treatment: 25%
I think most papers agree on this ratio - here we have pretty firm numbers.
Estimated mortality rate for everyone infected with Covid-19: 0,3% - 1,0%, depending on your age group.
If you’re in the group that gets diagnosed, multiply the mortality by 10. This is Case Fatality Ratio, which is the number we see quoted all over the media. So if you’re thinking 3% of the population will die of Covid-19 (which I’ve seen some tweets imply), no. That is not likely to happen, absent apocalypse-like scenarios.
The mortality rate depends on your age group (as previously documented), as well as medical treatment. With adequate capacity allowing for proper treatment, SST believes mortality rate can be kept close to 0,3% (CFR of 3%). If the health services are overwhelmed (Italian situation), obviously the mortality rate will be significantly worse. Note that CFR is always going to be a guesstimate during an outbreak (because the recovery or death of many cases are yet to be determined).
Numbers below from the WHO report.
Average length of the disease from onset of symptoms: 2 weeks.
Average length of the disease for hospitalized cases: 3 - 6 weeks.
Average length of the disease for fatal cases: 2 - 8 weeks.
Obviously, this is a heavy strain on health services, and explains why the situation in Italy broke down quickly (there is no quick hospitalization and out again) and why all health professionals are so worried. Also why the UK plan of trying to handle ~800K hospitalizations over a 3-4 month period is… optimistic to say the least.
Anyway, those are the latest numbers as I am aware of them. Feel free to correct me, if you find any newer/better numbers. If you’re interested in more numbers, check out CoVid-19 Research and Statistics. I’ve mostly gone with the numbers from SST above since they reflect the official estimates of DK’s top medical experts and seem more or less in line with the papers I’ve read, but that page collects a lot of the published statistics (and sources them), so you can check up for yourself.
