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How does testing positive for the flu rule out covid? What is to prevent someone from having both?
by meragrin_ 5y ago
How does testing positive for the flu rule out covid? What is to prevent someone from having both?
- GavinMcG 5y agoNo idea on the technical answer, but the healthcare logistics answer is that because it's not all that likely, a positive flu test was a decent stand-in when COVID tests weren't widely available.
- jtolmar 5y agoSay 1 in 10 people have flu and 1 in 10 have covid. In a population of 100, 9 have just flu, 9 have just covid, and 1 has both. Those 19 people present similar symptoms, and anyone among them has roughly a 53% chance of having each disease. They take a flu test and it comes up positive. Now they're either one of the 9 with just flu, or the one unlucky person with both, so there's only a 10% chance they have covid. The impact of this effect changes if has-flu and has-covid are correlated, but it's still there unless it's a 100% correlation.
- Matumio 5y agoThe technical term is "explaining away". If a burglar alarm goes off, you can be pretty sure someone triggered it. If there also was an earthquake at the same moment, you can be pretty sure of the opposite. Even though both events can happen at the same time.