I've been following the the death rate, because I think deaths are probably a more accurate statistic than cases - less likely that a covid19 death goes unreported.
This of course is a significantly lagging indicator, but it has been long enough that we can see social distancing is working.
Thing with deaths is that, as others have noted, many go unreported.
What I've looked at so far are IC admissions. As that depends the least on policy I think. Moreover, its the thing we most want to control (i.e. you want peak IC admissions not to go over IC capacity).
I've been using this to judge the effectiveness of measures taken in the Netherlands though. Which is quite different from using it to measure R_0 or R_t in other countries with other data.
> less likely that a covid19 death goes unreported
I don't think this is true at all. Many people die at home. Many die without having ever been officially tested. I've read that in some places the death toll is only counted from those who were tested and then died in a hospital.
Many people die all the time but it's much harder to hide how many people die total in a developed nation for systemic reasons. Except for natural disasters, the mortality rate for a country the size of the United States or Italy is surprisingly stable. The difference between deaths in March 2019 and March 2020 gives a lot more reliable information on the impact of the virus than testing numbers, which are limited by the availability of tests and the testing procedure (contact tracing vs testing only the highest risk patients or the most severe cases). However, this is just a more concrete measure of the extreme impact of the virus. Without a lot more data, it's not enough to even predict how many people have it or how infectious/deadly it is.
It's definitely still "less likely" that a death goes unreported versus an infection without a death. Both numbers are shit, but deaths likely less so.
I think deaths might be unreliable too, because 1) we don't know the mortality rate, we're extrapolating it from bad data and then using an extrapolated number to calculate a trend and 2) mortality rate would change between different groups, e.g. sick and old people vs healthy people, depending how infections spread.
That's why we're talking about deaths, not mortality. Mortality requires you to know the number of people who are infected which as stated above can be inaccurate because many people are not getting tested. However, it's less likely that a person who dies of pneumonia in hospital won't be tested. Also, there is likely to be a smaller proportion of deaths happening outside of hospitals than there are infections so you should consider the number of deaths to be more accurate than the number of cases.
> That's why we're talking about deaths, not mortality.
I believe you're confusing fatality and mortality. The correct version of that statement is: "That's why we're talking about mortality, not fatality.
The case fatality rate is the ratio of number of deaths to the number of people who are confirmed to have the disease (which depends a lot on standard of care, reporting, and bureaucratic integrity) whereas mortality rate is the rate of deaths in general.
Deaths are also unreliable because a) COVID-19 deaths are being reported differently as a notifiable disease (in the UK at least) as compared to, say, influenza and b) autopies are not being carried out on COVID-19 cases due to how contagious it is.
I agree 100% with Taek, and that's what I've been using - corona deaths instead of testing for months.
US testing is so porous as to be meaningless, even today.
Also, I care about bottlenecks like ventilators and ICU staff count, not the 98% of people who don't require hospitalization.
I find all US media and political coverage to completely miss the point, with anecdotes substituting for public health policy. It's like watching a train wreck that won't stop.
> US testing is so porous as to be meaningless, even today.
We've been testing well over 5000 people per day on average for over a month. Suppose 500 tests per day are randomly administered for the purpose of estimating overall prevalence of the virus. That sample ought to pretty clearly establish the total number of cases within 5%.
I'm sure there are some clever statisticians at the CDC with some fancy Bayesian inference or something who can push the confidence up even higher using all the non-randomly administered tests.
* deaths are also likely to be under reported (although, I agree, probably still better than the total unknown people who haven't been tested)
* a decreasing number of deaths does nothing to fix the actual problem: the possibility of contagion if we all resume normalish activity
My preferred metric has been 'average increase rate over 7 days', in other words, take the new detected cases any given day, calculate what percentage that is over the total for the last week, then average seven of those.
We'll never get a proper idea of how many people are actually infected until we get proper widespread testing, but at least we can get an idea of how bad cases (those that are likely to get tested) are growing. Another data point to look at is how many ICU units are in an area vs. how many ICU COVID cases there are and how many beds are still available. [1] San Francisco has finally started making those stats available:
That is people who test positive for Covid-19 who then die in hospital.
The other one collected by the office for national statistics is people who die where covid-19 is listed on the death certificate. There's some lag in those numbers.
It's hard to know how many deaths occur out of hospital, but it's possible about half of covid-19 deaths are happening in care homes. Covid-19 rips through care homes because the patients are by definition older and more frail; the staff have less PPE and less training in using PPE; the staff (in the UK) are often on very low pay which means they sometimes work in multiple homes; they carehomes sometimes have terrible sick pay terms.
(Lots of caveats, and care needed with these numbers, but)
> Key findings:
> Official data on the numbers of people affected by COVID-19 is not available in many countries
> Due to differences in testing availabilities and policies, and to different approaches to recording deaths, international comparisons are difficult
> Data from 3 epidemiological studies in the United States show that as many as half of people with COVID-19 infections in care homes were asymptomatic (or pre-symptomatic) at the time of testing
> Data from 5 European countries suggest that care home residents have so far accounted for between 42% and 57% of all deaths related to COVID-19.
As far as I have heard from Norway, not a single person that has been on a ventilator due to Covid-19 has died. The average age of the dead is 84 years old, which is a bit older than the average life expectancy in Norway. What I can gather from this information is that almost all deaths have happened in care homes or with older people who gets care at home.
This of course is a significantly lagging indicator, but it has been long enough that we can see social distancing is working.