Flattening the curve

Measures such as hand washing, social distancing, and the use of face masks help reduce and delay the peak number of active cases, thereby allowing more time for health care systems to prepare and respond more effectively to increased patient load. The time gained by "flattening the curve" can be used to "raise the line"—that is, to increase health care capacity in order to better meet surging demand.

Without containment measures—such as social distancing, vaccination, and the use of face masks—pathogens can spread exponentially. Early implementation of such interventions can reduce and delay the peak number of active cases, helping to protect a larger proportion of the population. This effect is often visualized through epidemic curves that demonstrate the benefits of early containment.

Flattening the curve is a public health strategy used to slow down the spread of an infectious disease in order to prevent overwhelming health care systems. The curve being flattened refers to the epidemic curve, a visual representation of the number of infected people needing health care over time. During an epidemic, health care systems can become overwhelmed when the number of people infected exceeds their capacity to provide adequate care. Flattening the curve reduces the peak number of infected people requiring care at any one time, helping ensure that the healthcare system remains within its capacity to treat patients. This strategy gained widespread attention during the early stages of the COVID-19 pandemic as governments sought to manage the spread of the SARS-CoV-2 virus.

The strategy relies on mitigation measures such as hand washing, use of face masks, and social distancing. A related concept is "raising the line", which involves increasing health care capacity – for example, by expanding the availability of intensive care unit (ICU) beds and ventilators. Flattening the curve and raising the line are complementary strategies that work together to reduce mortality and ensure the health care system can continue providing care.

Flattening the curve is distinct from "zero-COVID" strategies, which aim to eliminate transmission entirely. Instead, flattening the curve tolerates low levels of community transmission while aiming to minimize disruption and protect vulnerable populations. These strategies may be pursued sequentially or simultaneously during different phases of an epidemic, particularly as population-level immunity is acquired through infection or vaccination.