A key metric the share of coronavirus tests coming back positive shows how states' outbreaks have gotten out of control

Get the Full StoryThe US significantly scaled up its COVID-19 testing capacity after early missteps and prolonged delays.

As coronavirus cases in the US surge, one of the most important metrics to track a region's outbreak is its positivity rate: the share of tests that come back positive.

The WHO recommends stay-at-home orders if more than 5 of a region's tests come back positive over two weeks.

But 28 states have positivity rates above that threshold.

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The US's number of new COVID-19 cases grew by 27 last week compared to the week before.

President Donald Trump has suggested that the higher numbers are simply the product of increased testing, since more widely available diagnostic testing leads more cases to be caught and confirmed.See the rest of the story at Business InsiderNOW WATCH: Can you get the coronavirus twice?See Also:Harvard is keeping classes online this fall, placing it among the 8 of US colleges planning to do so. Here's the list so far.Gov. Greg Abbott just ordered residents of most Texas counties to wear face coverings in public. Those who don't could face a 250 fine.Elon Musk thinks the surge in coronavirus cases is due to testing errors, but a virologist is debunking that 'dangerous misinformation'