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Old 05-22-2020, 11:02 AM
Bootis is offline
Join Date: Jan 2007
Location: NYC
Posts: 1,664

Questions about Confirmed Cases, Total Tests and Brazil

Looking at the worldometers numbers, I'm wondering what to make of the numbers for total cases vs. total tests. Worldwide, the percentages of total cases from total tests seems surprisingly low, in the 7% - 12% range. US numbers fall right in that range, and knowing that for the most part, it seemed those who were able to be tested in the US were limited to the slam dunk obvious cases, and clearly vast numbers of people who did/do have COVID were not allowed to be tested, or never got tested for various reasons. Understood there's an error range in the test results, but it seems based on who was getting tested, the % of positive tests should be much, much higher, especially considering that it seems clear the majority of people who actually have/had it never got tested.

Brazil seems to be a single outlier, with a 42% positive result from total tests. (several other South American countries also have higher results in the 25% range, but nothing close to Brazil) What is different about Brazil (and lesser degree other South American countries) to be such an anomaly compared to all the other countries? Or is the number of tests data just completely useless noise?
Old 05-22-2020, 02:50 PM
AK84 is offline
Join Date: Apr 2008
Posts: 17,024
Testing numbers and percentage without context mean the square root of fuck all. Since these numbers are highly dependant on testing guidelines in force in the country.

If you are doingg what everyone was doing in March and the US is still doing, which is only test suspected cases according to specified testing criteria, then a high percentage of positive tests is very worrisome (the US was 1/5 in April and Italy was 1/2 during some of their worst days).

If you are doing extensive contact tracing, and attempting to identify people who have been exposed then a high percentage of positive tests is actually a good thing that shows you have correctly identified disease spread and you can quarantine and restrict access to hotspots (and identify further where hotpost might develop in the future).

Testing criteria have changed everywhere. Back in mid March everyplace outside of some places in East Asia had limited testing kit and testing criteria was that only those for whom symptoms and clinical signs were that of Covid should be tested. As testing capability has increased, this has changed.

In mid-March, 200 new positive tests meant most of those people who were very sick, needed hospitalization or at least significant medical attention. Today, 22nd May, 2000 new cases might mean that most of the people are asymptomatic or mildly symptomatic.

So the caveat about statistics is very much applicable.

Last edited by AK84; 05-22-2020 at 02:51 PM.


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