What Does “Flattening the Curve” Mean and Why is it Important?

The epidemic curve, a statistical chart used to visualize when and at what speed new cases of COVID-19 are reported, could be flattened instead of rising exponentially. Last week, the director of the National Institute of Allergy and Infectious Diseases brought up this idea — if we have less people infected, we would also have less deaths. “You do that by trying to interfere with the natural flow of the outbreak.”

The idea is to increase social distancing in order to slow the spread of the virus, so that you don’t get a huge spike in the number of people getting sick all at once. If that were to happen, there wouldn’t be enough hospital beds or mechanical ventilators for everyone who needs them, and the U.S. hospital system would be overwhelmed. That’s already happening in Italy.

If we can delay the spread of the virus so that new cases aren’t popping up all at once, but rather over the course of weeks or months, “then the system can adjust and accommodate all the people who are possibly going to get sick and possibly need hospital care.” People would still get infected but at a rate that the health care system could actually keep up with — a scenario represented by the more gently sloped curve on the graph. 

China took the extraordinary step of locking people down days before the Lunar New Year, to prevent the spread of the virus from Wuhan. The quarantine appears to have prevented explosive outbreaks from occurring in cities outside of the Hubei province, where Wuhan is located. The spread has since slowed in China as well as in South Korea (the third largest outbreak outside of China), however Italy and Iran are having difficulties with containment. 

Any cases that can be prevented and any transmissions that can be avoided will have an enormous impact on lessening the spread and therefore help health systems remain functional. On any normal day, health systems in the US typically run close to capacity. If a hospital is overrun by COVID-19 patients, these patients will have a lower chance of surviving than if they became ill when the hospital’s load was more manageable. All of the other patients (car crashes, cancer, pregnancies with complications) also risk getting a less caliber of care when the health system is trying to cope with an outbreak.

If we are able to “slow” the outbreak so that the number of cases is spread over time instead of happening all at once, health care professionals will be better equipped to handle cases. Coronavirus has shed light on the risk of our health care infrastructure pulling apart at the seams if the virus spreads too quickly.

The countries and regions that have been hit by the virus report that hospitals are swamped with the influx of sick people struggling to breathe and having to decide who to try to save. Italy followed China’s example and put its population on lockdown to hopefully not spread the virus.

“If a Wuhan-like outbreak were to take place in a U.S. city, even with strong social distancing and contact tracing protocols as strict as Wuhan lockdown, hospitalization and ICU needs from COVID-19 patients alone may exceed current capacity. So it is essential to ‘bend the curve’.”

Measures such as banning concerts, sporting events and other mass gatherings, closing schools, increasing telecommuting efforts and cities closing restaurants will help to slow the spread. The sooner these measures are implemented, the more effective they can be. 

Decision makers have had a hard time pulling the trigger on these difficult, impactful decisions due to the lack of data and evidence of widespread transmission. However, according to epidemiologists, this is precisely the time when public health measures of this sort can have an impact.

Some Asian countries have had a less severe outbreak than European countries. While this is speculation, the cause could be due to the SARS outbreak of 2003 which hit Asia hard. When news of a new SARS-like virus came about, these countries already were well aware of what social distancing meant and were able to lean into these measures that the US is now starting to implement. In these Asian countries, there are not only less COVID-19 illnesses but also less diarrheal and conjunctivitis infections which also spread person to person. Social distancing does seem to be a driver in these countries that are experiencing less cases.

Johns Hopkins University experts are sharing knowledge on this global public health issue. You can find more information at coronavirus.jhu.edu.