Don’t Be Fooled by America’s Flattening Curve
Here is America’s coronavirus curve: the number of newly reported cases each day. The curve has started declining moderately from the peak in early April.
But that’s not the whole story. Separate the region around New York City and the picture becomes far less rosy.
Also remove the regions around Detroit and New Orleans — other cities with large outbreaks in early April — and the national trend is clearer: After a brief plateau, cases in America continue to climb.
Here is America’s coronavirus curve: the number of newly reported cases each day. The curve has started declining moderately from the peak in early April.
During the early days of the pandemic, the public’s attention was fixed on various models, each showing a steep upswing, with cases steadily increasing each day, followed by the tail-end of the curve as cases fade away.
Americans saw, with increasing dread, the predicted upswing in the national numbers. Then, over the last couple of weeks, it stopped.
And yet, forecasters are projecting even more deaths on the horizon. A leaked document obtained by The New York Times projected more than 3,000 people could die each day by the end of May. Another historically conservative model, favored by the Trump administration, just doubled its projected death toll, too.
The tail-end of the national epidemic is not materializing.
“If you just look at the total number of cases, you’re going to miss what’s underneath it,” said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. “It’s not a leveling-off. It’s a painful handoff.”
America’s current “plateau” isn’t good news, he said. Infections from the earliest-hit metropolitan areas are now spawning outbreaks of their own across the country.
What’s happening is a series of “mini-epidemics,” each following the predictable curve that rises and falls as the virus runs out of susceptible people to infect, he said. Meanwhile, the national numbers offer a deceptive picture: All the mini-epidemics are laid on top of one another, coming at different moments and infecting different populations.
The pattern is repeating in states all across the country, with new outbreaks emerging after the initial, localized epidemic waned. These mini-epidemics take off regionally and put hundreds of lives at risk while the statewide numbers appear to be flat or dropping.
Consider Oklahoma and Texas, two states that loosened their restrictions on businesses statewide. Each state made it through an early spike and watched the number of cases fall for weeks.
Hiding behind the statewide numbers was a different story. Oklahoma’s early spike was due to a surge of cases in its largest cities. Statewide numbers fell during the recovery — but this was due only to the tail-end of outbreaks around Tulsa and Oklahoma City. When those areas are excluded from the statewide figures, the number of new cases holds steady before rising once again.
The same is true in Texas: Cases spiked early on because of a surge in Houston, and after the city's peak, the state seemed to be improving. But removing Houston from the statewide figures shows the number of new cases was rising all along.
Some states are taking the local nature of their outbreaks into consideration and have adjusted their plans to reopen accordingly.
Indiana is also reopening, but not in Cass, Lake and Marion Counties. Even still, cases are still trending up in the rest of the state.
Florida had a huge spike in cases around Miami after spring break revelry in March. Florida is beginning to relax the shutdown across most of the state, but not in Miami-Dade, Broward and Palm Beach Counties. Unlike Indiana, cases are falling in most parts of the state.
Note: Shutdown counties for Indiana include Cass, Lake and Marion Counties. For Florida, they include Miami-Dade, Broward and Palm Beach Counties.
State and local leaders shouldn’t expect that their epidemics are over just because the state passed an initial peak several weeks ago. Neither should the White House, which is planning to wind down its coronavirus task force.
The nature of disease transmission demands that public officials be mindful of how outbreaks are progressing in certain areas, not just how the state looks over all. Plans to reopen premised on a steady number of cases statewide ignore the mini-epidemics keeping the numbers from dropping sharply. Monitoring epidemics on a local level are key to tailoring reopening plans that won’t result in the virus spreading just as fast as in early April.
And America has a long way to go, Dr. Osterholm said, as the virus spreads to infectable hosts.
“One day this peak will look relatively small compared to the activity we will see coming down the pike,” he said. “That’s inevitable.”
Charts show 7-day rolling averages of newly reported cases each day. Data for Houston, Tulsa and Oklahoma City extends to counties within their respective core-based statistical area. Data for New York City, Detroit and New Orleans uses data reported in counties in the corresponding combined statistical areas. Get the Times data used here.
Nathaniel Lash is a graphics reporter for the Opinion section.
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By Nathaniel Lash
May 6, 2020 (Accessed July 2020 )
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