Flattening the curve refers to community isolation measures that keep the daily number of disease cases at a manageable level for medical providers.
(Image: © CDC)
Efforts to completely contain the new coronavirus — the pandemic responsible for infecting hundreds of thousands of people in 130 countries with the disease, called COVID-19 — have failed. 

In less than a month, the global number of confirmed COVID-19 cases doubled from about 75,000 cases on Feb. 20 to more than 153,000 on March 15. That infection rate, scary as it sounds, hides just how much the out-of-control virus has spread, especially in the hardest-hit communities. In Italy, for example — the country with the worst COVID-19 outbreak outside of China — confirmed cases doubled from 10,000 to 20,000 in just four days (March 11 to March 15). 

This rapid growth rate in Italy has already filled some hospitals there to capacity, forcing emergency rooms to close their doors to new patients, hire hundreds of new doctors and request emergency supplies of basic medical equipment, like respirator masks, from abroad. This lack of resources contributes, in part, to the outsize COVID-19 death rate in Italy, which is roughly 7% — double the global average, PBS reported.

Related: Live updates on COVID-19

Health officials take for granted that COVID-19 will continue to infect millions of people around the world over the coming weeks and months. However, as the outbreak in Italy shows, the rate at which a population becomes infected makes all the difference in whether there are enough hospital beds (and doctors, and resources) to treat the sick. 

In epidemiology, the idea of slowing a virus' spread so that fewer people need to seek treatment at any given time is known as "flattening the curve." It explains why so many countries are implementing "social distancing" guidelines — including a "shelter in place" order that affects 6.7 million people in Northern California, even though COVID-19 outbreaks there might not yet seem severe.

Here's what you need to know about the curve, and why we want to flatten it.

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