Apr 29, 2020 - Health

Not all states are behind on coronavirus testing

Data: The COVID Tracking Project, U.S. Census Bureau; Chart: Andrew Witherspoon/Axios
Data: The COVID Tracking Project, U.S. Census Bureau; Chart: Andrew Witherspoon/Axios

Some states — generally those without major coronavirus outbreaks — are doing enough testing for now, at least according to one metric.

Between the lines: Although the U.S. as a whole still falls far short of where it needs to be on testing, several individual states are testing enough people to put their positive rate at or below 10% of the total number of people tested — an important indicator of whether the state can successfully identify new outbreaks.

The big picture: The World Health Organization has recommended that coronavirus testing should be prolific enough that only 10% or less of the tests come back positive, according to NPR, although some experts say the rate should be even lower.

  • That indicates that a large enough testing net is being cast to catch all of the infections in the community, which is key to then stopping the spread of the virus.
  • “If you have a very high positive rate, it means that there are probably a good number of people out there who have the disease who you haven’t tested,” Ashish Jha, director of the Harvard Global Health Institute, recently told the New York Times.
  • “You want to drive the positive rate down, because the fundamental element of keeping our economy open is making sure you’re identifying as many infected people as possible and isolating them," he added.

Yes, but: Outbreaks are not static, and states that are testing a small portion of their population, yet have a low positive rate, could be overwhelmed by cases down the road.

Testing shortages have led to tests generally being reserved for health care workers and the sickest patients, meaning that a lot of mildly symptomatic or asymptomatic people aren't being tested at all.

  • We're also not yet doing surveillance testing on the scale needed.
  • Some states — like New York or Massachusetts — are completing more tests than others after adjusting for population, but still have a higher positivity rate. That means that those states have a much larger caseload than others, and thus need to test more.

What we're watching: As states begin to lift social distancing measures, those who do so while their positive rate is still high will be particularly vulnerable to new outbreaks.

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