4 ms·

IMO this looks to by a symptom of lack of testing. Overall the ratio of tests coming back positive is unchanged: https://raw.githubusercontent.com/lettergram/c

IMO this looks to by a symptom of lack of testing. Overall the ratio of tests coming back positive is unchanged: https://raw.githubusercontent.com/lettergram/covid19-analysis/master/graphs/us-test-ratios.png https://raw.githubusercontent.com/lettergram/covid19-analysi... Even though we are doing more tests. Meaning the reduction in speed-of-spread likely has more to do with lack of testing. That being said, I’m sure spread is being reduced, we just don’t know to what extent because we don’t have enough effective testing. It’s also possible (probably likely) our tests are not exceptionally accurate. It’s the best we have, but given all of this is <6 months old the false positive/negative rate can be high. Generally, Testing isn’t an effective way to measure spread. Probably we should use “hospitalizations with flu symptoms“ as the best indicator. You can compare testing per state and deaths here: Tests: https://raw.githubusercontent.com/lettergram/covid19-analysis/master/graphs/us-tests-by-state.png https://raw.githubusercontent.com/lettergram/covid19-analysi... Deaths: https://raw.githubusercontent.com/lettergram/covid19-analysis/master/graphs/us-deaths-by-state.png https://raw.githubusercontent.com/lettergram/covid19-analysi... Overall repo: https://github.com/lettergram/covid19-analysis https://github.com/lettergram/covid19-analysis

usaar333 7y ago
Correct. Testing is only a good measurement with massive testing, even randomized testing. Iceland's data is probably the closest to actual infections and many states probably look similar. (https://www.covid.is/data https://www.covid.is/data)
zaroth 7y ago
The reported specificity and sensitivity of RT-PCR testing is quite good, but obviously not 100%. RT-PCR is considered the "gold standard" in viral testing. If you want to contact trace, we would need many orders of magnitude more testing. If you want to know prevalence over time, and therefore Rt, we could ascertain it very accurately with much less testing, but it would need to be done against statistically valid and unbiased random samples of the population, not at all what is going on today. Since the testing we are doing today doesn't really satisfy either condition, and there's also no front-line approved treatments for those that are definitively diagnosed (rather, we treat the symptoms, which are self-evident), frankly I'm not sure I understand the extreme focus on testing.
- sjg007 7y ago
  These tests have a false negative rate of 30%
  - zaroth 7y ago
    My understanding is that it’s under 10% false negative and false positive typically for this type of testing. Other tests like the rapid saliva test are totally different.
    - sjg007 7y ago
      False negative is higher.
- nitrogen 7y ago
  I'm not sure I understand the extreme focus on testing. 3blue1brown on YouTube created a simple model that suggests that testing and quarantine of positive cases is the most effective way to slow the spread (within the simplified model). Testing should allow us to isolate just the infected, and ease off the restrictions on others.
  - ethbro 7y ago
    With statistically valid random testing, even detecting clusters / communities (as opposed to individuals) and clearing same would be conducive to reopening the economy. Unfortunately, the path to doing so "I'm going to force you to get tested, despite you having no symptoms" is political anathema.
    - aianus 7y ago
      > "I'm going to force you to get tested, despite you having no symptoms" is political anathema This seems less extreme and more palatable than "I'm going to force you to stay home and lose your job, despite you having no symptoms" which is very nonetheless popular right now.
    - 7y ago
kevingadd 7y ago
"hospitalizations with flu symptoms" is a good indicator, but you have to account for the fact that people who catch it in different areas (or with different incomes) will have different levels of access to a hospital. many people are dying (or recovering) at home.
- Retric 7y ago
  Not just that. NYC has seen the number of people dying at home increase from around 20 per day to 200 per day. The difference is likely a mix of COVID-19 cases, people not seeking treatment out of fear, and people just spending significantly more time at home. But, that kind of change makes accurate statistics even more difficult.
- projektfu 7y ago
  Just read an interesting article using ICU admissions as a proxy. Of course it does lag, but it may be more consistent than hospital admissions. http://medrxiv.org/cgi/content/short/2020.04.13.20063388 http://medrxiv.org/cgi/content/short/2020.04.13.20063388
  - dmurray 7y ago
    It does saturate at some point, though. If you're turning patients away who are in need of ICU treatment (as some Italian hospitals were), your ICU admissions will be constant and equal to your rate of release from ICU, so it will appear that you've "flattened the curve" even if the number of sick people continues to grow exponentially.
    - projektfu 7y ago
      True, the paper talks about patients needing ICU, if you can get that statistic instead.

usaar333 7y ago

Correct. Testing is only a good measurement with massive testing, even randomized testing. Iceland's data is probably the closest to actual infections and many states probably look similar. (https://www.covid.is/data https://www.covid.is/data)

zaroth 7y ago

The reported specificity and sensitivity of RT-PCR testing is quite good, but obviously not 100%. RT-PCR is considered the "gold standard" in viral testing. If you want to contact trace, we would need many orders of magnitude more testing. If you want to know prevalence over time, and therefore Rt, we could ascertain it very accurately with much less testing, but it would need to be done against statistically valid and unbiased random samples of the population, not at all what is going on today. Since the testing we are doing today doesn't really satisfy either condition, and there's also no front-line approved treatments for those that are definitively diagnosed (rather, we treat the symptoms, which are self-evident), frankly I'm not sure I understand the extreme focus on testing.

sjg007 7y ago
These tests have a false negative rate of 30%
- zaroth 7y ago
  My understanding is that it’s under 10% false negative and false positive typically for this type of testing. Other tests like the rapid saliva test are totally different.
  - sjg007 7y ago
    False negative is higher.
nitrogen 7y ago
I'm not sure I understand the extreme focus on testing. 3blue1brown on YouTube created a simple model that suggests that testing and quarantine of positive cases is the most effective way to slow the spread (within the simplified model). Testing should allow us to isolate just the infected, and ease off the restrictions on others.
- ethbro 7y ago
  With statistically valid random testing, even detecting clusters / communities (as opposed to individuals) and clearing same would be conducive to reopening the economy. Unfortunately, the path to doing so "I'm going to force you to get tested, despite you having no symptoms" is political anathema.
  - aianus 7y ago
    > "I'm going to force you to get tested, despite you having no symptoms" is political anathema This seems less extreme and more palatable than "I'm going to force you to stay home and lose your job, despite you having no symptoms" which is very nonetheless popular right now.
  - 7y ago

kevingadd 7y ago

"hospitalizations with flu symptoms" is a good indicator, but you have to account for the fact that people who catch it in different areas (or with different incomes) will have different levels of access to a hospital. many people are dying (or recovering) at home.

Retric 7y ago
Not just that. NYC has seen the number of people dying at home increase from around 20 per day to 200 per day. The difference is likely a mix of COVID-19 cases, people not seeking treatment out of fear, and people just spending significantly more time at home. But, that kind of change makes accurate statistics even more difficult.
projektfu 7y ago
Just read an interesting article using ICU admissions as a proxy. Of course it does lag, but it may be more consistent than hospital admissions. http://medrxiv.org/cgi/content/short/2020.04.13.20063388 http://medrxiv.org/cgi/content/short/2020.04.13.20063388
- dmurray 7y ago
  It does saturate at some point, though. If you're turning patients away who are in need of ICU treatment (as some Italian hospitals were), your ICU admissions will be constant and equal to your rate of release from ICU, so it will appear that you've "flattened the curve" even if the number of sick people continues to grow exponentially.
  - projektfu 7y ago
    True, the paper talks about patients needing ICU, if you can get that statistic instead.