Flattening the curve

Last updated

20200403 Flatten the curve animated GIF.gif
Measures such as hand washing, social distancing and face masks reduce and delay the peak of active cases, allowing more time for healthcare capacity to increase and better cope with patient load. [1] Time gained through thus flattening the curve can be used to raise the line of healthcare capacity to better meet surging demand. [2]
20200609 Effect of pandemic containment measures.gif
Without pandemic containment measures—such as social distancing, vaccination, and use of face masks—pathogens can spread exponentially. [3] This graphic illustrates how early adoption of containment measures tends to protect wider swaths of the population, thus reducing and delaying the peak of active cases.
SIR model showing the impact of reducing the infection rate (
{\textstyle \beta }
) by 76% SIR model anim.gif
SIR model showing the impact of reducing the infection rate () by 76%

Flattening the curve was a public health strategy to slow down the spread of the SARS-CoV-2 virus during the early stages of the COVID-19 pandemic. The curve being flattened is the epidemic curve, a visual representation of the number of infected people needing health care over time. During an epidemic, a health care system can break down when the number of people infected exceeds the capability of the health care system's ability to take care of them. Flattening the curve means slowing the spread of the epidemic so that the peak number of people requiring care at a time is reduced, and the health care system does not exceed its capacity. Flattening the curve relies on mitigation techniques such as hand washing, use of face masks and social distancing.


A complementary measure is to increase health care capacity, to "raise the line". [4] As described in an article in The Nation , "preventing a health care system from being overwhelmed requires a society to do two things: 'flatten the curve'—that is, slow the rate of infection so there aren't too many cases that need hospitalization at one time—and 'raise the line'—that is, boost the hospital system's capacity to treat large numbers of patients." [5] During 2020, in the early stages of the COVID-19 pandemic, two key measures were to increase the numbers of available ICU beds and ventilators, which were in systemic shortage. [2] [ needs update ]

Experts differentiate between "zero-COVID", which is an elimination strategy taken by China, and "flattening the curve", a mitigation strategy that attempts to lessen the effects of the virus on society as much as possible, but still tolerates low levels of transmission within the community. [6] [7] These two initial strategies can be pursued sequentially or simultaneously during the acquired immunity phase through natural and vaccine-induced immunity. [8]


Warnings about the risk of pandemics were repeatedly made throughout the 2000s and the 2010s by major international organisations including the World Health Organization (WHO) and the World Bank, especially after the 2002–2004 SARS outbreak. [9] Governments, including those in the United States and France, both prior to the 2009 swine flu pandemic, and during the decade following the pandemic, both strengthened their health care capacities and then weakened them. [10] [11] At the time of the COVID-19 pandemic, health care systems in many countries were functioning near their maximum capacities. [4] [ better source needed ]

In a situation like this, when a sizable new epidemic emerges, a portion of infected and symptomatic patients create an increase in the demand for health care that has only been predicted statistically, without the start date of the epidemic nor the infectivity and lethality known in advance. [4] If the demand surpasses the capacity line in the infections per day curve, then the existing health facilities cannot fully handle the patients, resulting in higher death rates than if preparations had been made. [4]

An influential UK study showed that an unmitigated COVID-19 response in the UK could have required up to 46 times the number of available ICU beds. [12] One major public health management challenge is to keep the epidemic wave of incoming patients needing material and human health care resources supplied in a sufficient amount that is considered medically justified. [4]

Flattening the curve

Queue markers at a shopping mall in Bangkok as a social distancing practicing Queue during COVID-19 must be social distancing at ICONSIAM.jpg
Queue markers at a shopping mall in Bangkok as a social distancing practicing

Non-pharmaceutical interventions such as hand washing, social distancing, isolation and disinfection [4] reduce the daily infections, therefore flattening the epidemic curve. A successfully flattened curve spreads health care needs over time and the peak of hospitalizations under the health care capacity line. [2] Doing so, resources, be it material or human, are not exhausted and lacking. In hospitals, it for medical staff to use the proper protective equipment and procedures, but also to separate contaminated patients and exposed workers from other populations to avoid patient-to-doctor or patient-to-patient spreading. [4]

Raising the line

Along with the efforts to flatten the curve is the need for a parallel effort to "raise the line", to increase the capacity of the health care system. [2] Healthcare capacity can be raised by raising equipment, staff, providing telemedicine, home care and health education to the public. [4] Elective procedures can be cancelled to free equipment and staffs. [4] Raising the line aims to provide adequate medical equipment and supplies for more patients. [13]

During the COVID-19 pandemic

Simulations comparing rate of spread of infection, and number of deaths due to overrun of hospital capacity, when social interactions are "normal" (left, 200 people moving freely) and "distanced" (right, 25 people moving freely).
Green = Healthy, uninfected individuals
Red = Infected individuals
Blue = Recovered individual
Black = Dead individuals Katapult importance social distancing.gif
Simulations comparing rate of spread of infection, and number of deaths due to overrun of hospital capacity, when social interactions are "normal" (left, 200 people moving freely) and "distanced" (right, 25 people moving freely).
Green = Healthy, uninfected individuals
Red = Infected individuals
Blue = Recovered individual
Black = Dead individuals

The concept was popular during the early months of the COVID-19 pandemic. [15]

According to Vox, in order to move away from social distancing and return to normal, the US needs to flatten the curve by isolation and mass testing, and to raise the line. [16] Vox encourages building up health care capability including mass testing, software and infrastructures to trace and quarantine infected people, and scaling up cares including by resolving shortages in personal protection equipment, face masks. [16]

According to The Nation, territories with weak finances and health care capacity such as Puerto Rico face an uphill battle to raise the line, and therefore a higher imperative pressure to flatten the curve. [5]

In March 2020, UC Berkeley Economics and Law professor Aaron Edlin commented that ongoing massive efforts to flatten the curve supported by trillions dollars emergency package should be matched by equal efforts to raise the line and increase health care capacity. [17] Edlin called for an activation of the Defense Production Act to order manufacturing companies to produce the needed sanitizers, personal protective equipment, ventilators, and set up hundreds thousands to millions required hospital beds. [17] Standing in March 2020 estimates, Edlin called for the construction of 100-300 emergency hospitals to face what he described as "the largest health catastrophe in 100 years" and to adapt health care legislation preventing emergency practices needed in time of pandemics. [17] Edlin pointed out proposed stimulus package as oriented toward financial panics, while not providing sufficient funding for the core issue of a pandemic: health care capability. [17]

By 2021, the phrase "flatten the curve" had largely fallen out of medical messaging etymology. [18] [19]

See also

Related Research Articles

<span class="mw-page-title-main">Ventilator</span> Device that provides mechanical ventilation to the lungs

A ventilator is a piece of medical technology that provides mechanical ventilation by moving breathable air into and out of the lungs, to deliver breaths to a patient who is physically unable to breathe, or breathing insufficiently. Ventilators are computerized microprocessor-controlled machines, but patients can also be ventilated with a simple, hand-operated bag valve mask. Ventilators are chiefly used in intensive-care medicine, home care, and emergency medicine and in anesthesiology.

<span class="mw-page-title-main">COVID-19 pandemic</span> Ongoing global pandemic of coronavirus disease 2019

The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identified from an outbreak in Wuhan, China, in December 2019. Attempts to contain it there failed, allowing the virus to spread to other areas of China and later worldwide. The World Health Organization (WHO) declared the outbreak a public health emergency of international concern on 30 January 2020 and a pandemic on 11 March 2020. As of 26 October 2022, the pandemic had caused more than 628 million cases and 6.58 million confirmed deaths, making it one of the deadliest in history.

<span class="mw-page-title-main">Social impact of the COVID-19 pandemic</span> Indirect effects of the COVID-19 pandemic

The COVID-19 pandemic has had far-reaching consequences beyond the spread of the disease itself and efforts to quarantine it, including political, cultural, and social implications.

<span class="mw-page-title-main">COVID-19 pandemic in Taiwan</span> Ongoing COVID-19 viral pandemic in Taiwan

The COVID-19 pandemic in Taiwan is part of the worldwide pandemic of coronavirus disease 2019 caused by severe acute respiratory syndrome coronavirus 2. As of 25 October 2022, 27,461,767 tests had been conducted in Taiwan, of which 7,515,630 are confirmed cases, including 12,427 deaths.

<span class="mw-page-title-main">COVID-19 pandemic in the United Kingdom</span> Ongoing viral pandemic

The COVID-19 pandemic in the United Kingdom is a part of the worldwide pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In the United Kingdom, it has resulted in 23,855,526 confirmed cases, and is associated with 208,497 deaths.

<span class="mw-page-title-main">COVID-19 pandemic in Poland</span> Ongoing COVID-19 viral pandemic in Poland

The COVID-19 pandemic in Poland is part of the worldwide pandemic of coronavirus disease 2019 caused by severe acute respiratory syndrome coronavirus 2. In February and March 2020, health authorities in Poland carried out laboratory testing of suspected cases of infection by SARS-CoV-2, as well as home quarantining and monitoring. On 4 March 2020, the first laboratory confirmed case in Poland was announced in a man hospitalised in Zielona Góra. On March 10, 2020, the World Health Organization declared the local transmission phase of SARS-CoV-2 in Poland. On March 12, 2020, the first death from coronavirus disease 2019 (COVID-19) in Poland was that of a 56-year-old woman.

<span class="mw-page-title-main">COVID-19 pandemic in Belgium</span> Ongoing COVID-19 viral pandemic in Belgium

The COVID-19 pandemic in Belgium has resulted in 4,607,296 confirmed cases of COVID-19 and 32,883 deaths.

<span class="mw-page-title-main">COVID-19 pandemic in the Czech Republic</span> Ongoing COVID-19 viral pandemic in the Czech Republic

The COVID-19 pandemic in the Czech Republic is part of the worldwide pandemic of coronavirus disease 2019 caused by severe acute respiratory syndrome coronavirus 2. The first three confirmed cases in the Czech Republic were reported on 1 March 2020. On 12 March, the government declared a state of emergency, for the first time in the country's modern history for the area of the entire country. On 16 March, the country closed its borders, forbade the entry of foreigners without residence permits, and issued a nationwide curfew. While originally planned to be in effect until 24 March, the measures were later extended until 1 April and then again until the end of State of Emergency which was extended by the Chamber of Deputies until 30 April 2020 and then again until 17 May 2020.

<span class="mw-page-title-main">COVID-19 pandemic in Slovenia</span> Ongoing COVID-19 viral pandemic in Slovenia

The COVID-19 pandemic in Slovenia is part of the pandemic of coronavirus disease 2019 caused by severe acute respiratory syndrome coronavirus 2. The virus spread to Slovenia on 4 March 2020, when the first case was confirmed. It was an imported case transmitted by a tourist traveling from Morocco via Italy, which was the center of the SARS-CoV-2 in Europe at the time.

<span class="mw-page-title-main">COVID-19 pandemic in California</span> Ongoing COVID-19 viral pandemic in California, United States

Ten of the first twenty confirmed COVID-19 cases in the United States occurred in California, the first of which was confirmed on January 26, 2020. All of the early confirmed cases were persons who had recently travelled to China, as testing was restricted to this group. On January 29, 2020, as disease containment protocols were still being developed, the U.S. Department of State evacuated 195 persons from Wuhan, China aboard a chartered flight to March Air Reserve Base in Riverside County, and in the process may have contributed to spread within the state and the US at large. On February 5, 2020, the U.S. evacuated 345 more citizens from Hubei Province to two military bases in California, Travis Air Force Base in Solano County and Marine Corps Air Station Miramar, San Diego, where they were quarantined for 14 days. A state of emergency was declared in the state on March 4, 2020. A mandatory statewide stay-at-home order was issued on March 19, 2020, that was ended on January 25, 2021. On April 6, 2021, the state announced plans to fully reopen the economy by June 15, 2021.

<span class="mw-page-title-main">COVID-19 pandemic in Scotland</span> Ongoing COVID-19 viral pandemic in Scotland

The COVID-19 pandemic in Scotland is part of the COVID-19 pandemic of coronavirus disease-2019, caused by the virus SARS-CoV-2. The first case of COVID-19 was confirmed in Scotland on 1 March 2020. Community transmission was first reported on 11 March 2020, and the first confirmed death was on 13 March 2020.

<span class="mw-page-title-main">Shortages related to the COVID-19 pandemic</span> Medical material and other goods shortages caused by the COVID-19 pandemic

Shortages of medical materials, manufacturing and consumer goods caused by the COVID-19 pandemic quickly became a major issue worldwide, as did interruptions to the global supply chain, which has challenged supply chain resilience across the globe. Shortages of personal protective equipment, such as medical masks and gloves, face shields, and sanitizing products, along with hospital beds, ICU beds, oxygen therapy equipment, ventilators, and ECMO devices were reported in most countries.

Exercise Cygnus was a three-day simulation exercise carried out by the UK Government in October 2016 to estimate the impact of a hypothetical H2N2 influenza pandemic on the United Kingdom. It aimed to identify strengths and weaknesses within the United Kingdom health system and emergency response chain by putting it under significant strain, providing insight on the country's resilience and any future ameliorations required. It was conducted by Public Health England representing the Department of Health and Social Care, as part of a project led by the "Emergency Preparedness, Resilience and Response Partnership Group". Twelve government departments across Scotland, Wales and Northern Ireland, as well as local resilience forums (LRFs) participated. More than 950 workers from those organisations, prisons and local or central government were involved during the three-day simulation, and their ability to cope under situations of high medical stress was tested.

Planning and preparing for pandemics has happened in countries and international organizations. The World Health Organization writes recommendations and guidelines, though there is no sustained mechanism to review countries' preparedness for epidemics and their rapid response abilities. National action depends on national governments. In 2005–2006, before the 2009 swine flu pandemic and during the decade following it, the governments in the United States, France, UK, and others managed strategic health equipment stocks, but they often reduced stocks after the 2009 pandemic in order to reduce costs.

In epidemiology, a non-pharmaceutical intervention (NPI) is any method used to reduce the spread of an epidemic disease without requiring pharmaceutical drug treatments. Examples of non-pharmaceutical interventions that reduce the spread of infectious diseases include wearing a face mask and staying away from sick people.

<span class="mw-page-title-main">Impact of the COVID-19 pandemic on healthcare workers</span>

The COVID-19 pandemic has impacted healthcare workers physically and psychologically. Healthcare workers are more vulnerable to COVID-19 infection than the general population due to frequent contact with infected individuals. Healthcare workers have been required to work under stressful conditions without proper protective equipment, and make difficult decisions involving ethical implications. Health and social systems across the globe are struggling to cope. The situation is especially challenging in humanitarian, fragile and low-income country contexts, where health and social systems are already weak. Services to provide sexual and reproductive health care risk being sidelined, which will lead to higher maternal mortality and morbidity.

<span class="mw-page-title-main">Public health mitigation of COVID-19</span> Measures to halt the spread of the respiratory disease among populations

Speed and scale are key to mitigation of COVID-19, due to the fat-tailed nature of pandemic risk and the exponential growth of COVID-19 infections. For mitigation to be effective, (a) chains of transmission must be broken as quickly as possible through screening and containment, (b) health care must be available to provide for the needs of those infected, and (c) contingencies must be in place to allow for effective rollout of (a) and (b).

<span class="mw-page-title-main">United States responses to the COVID-19 pandemic</span> Actions by the United States regarding the COVID-19 pandemic

The United States' response to the COVID-19 pandemic with consists of various measures by the medical community; the federal, state, and local governments; the military; and the private sector. The public response has been highly polarized, with partisan divides being observed and a number of concurrent protests and unrest complicating the response.

<span class="mw-page-title-main">United Kingdom responses to the COVID-19 pandemic</span> Actions by the United Kingdom regarding the COVID-19 pandemic

The United Kingdom's response to the COVID-19 pandemic consists of various measures by the healthcare community, the British and devolved governments, the military and the research sector.


  1. Wiles, Siouxsie (9 March 2020). "The three phases of Covid-19—and how we can make it manageable". The Spinoff . Morningside, Auckland, New Zealand. Archived from the original on 27 March 2020. Retrieved 9 March 2020.
  2. 1 2 3 4 Barclay, Eliza (7 April 2020). "Chart: The US doesn't just need to flatten the curve. It needs to "raise the line."". Vox . Archived from the original on 7 April 2020. Retrieved 7 April 2020.
  3. Maier, Benjamin F.; Brockmann, Dirk (15 May 2020). "Effective containment explains subexponential growth in recent confirmed COVID-19 cases in China". Science. 368 (6492): 742–746. Bibcode:2020Sci...368..742M. doi:10.1126/science.abb4557. PMC   7164388 . PMID   32269067. ("...initial exponential growth expected for an unconstrained outbreak.")
  4. 1 2 3 4 5 6 7 8 9 Beating Coronavirus: Flattening the Curve, Raising the Line (YouTube video). Retrieved 12 April 2020.
  5. 1 2 Gelardi, Chris (9 April 2020). "Colonialism Made Puerto Rico Vulnerable to Coronavirus Catastrophe". The Nation . ISSN   0027-8378. Archived from the original on 12 April 2020. Retrieved 12 April 2020.
  6. Oliu-Barton, Miquel; Pradelski, Bary S R; Aghion, Philippe; Artus, Patrick; Kickbusch, Ilona; Lazarus, Jeffrey V; Sridhar, Devi; Vanderslott, Samantha (28 April 2021). "SARS-CoV-2 elimination, not mitigation, creates best outcomes for health, the economy, and civil liberties". The Lancet. 397 (10291): 2234–2236. doi:10.1016/S0140-6736(21)00978-8. PMC   8081398 . PMID   33932328.
  7. Li, Zhongjie; Chen, Qiulan; Feng, Luzhao; Rodewald, Lance; Xia, Yinyin; Yu, Hailiang; Zhang, Ruochen; An, Zhijie; Yin, Wenwu; Chen, Wei; Qin, Ying; Peng, Zhibin; Zhang, Ting; Ni, Daxin; Cui, Jinzhao; Wang, Qing; Yang, Xiaokun; Zhang, Muli; Ren, Xiang; Wu, Dan; Sun, Xiaojin; Li, Yuanqiu; Zhou, Lei; Qi, Xiaopeng; Song, Tie; Gao, George F; Feng, Zijian (4 June 2020). "Active case finding with case management: the key to tackling the COVID-19 pandemic". The Lancet. 396 (10243): 63–70. doi:10.1016/S0140-6736(20)31278-2. PMC   7272157 . PMID   32505220.
  8. Bhopal, Raj S (9 September 2020). "To achieve "zero covid" we need to include the controlled, careful acquisition of population (herd) immunity". BMJ. 370: m3487. doi:10.1136/bmj.m3487. eISSN   1756-1833. PMID   32907816. S2CID   221538577.
  9. "Wanted: world leaders to answer the coronavirus pandemic alarm". South China Morning Post. 31 March 2020. Archived from the original on 9 April 2020. Retrieved 6 April 2020.
  10. Manjoo, Farhad (25 March 2020). "Opinion | How the World's Richest Country Ran Out of a 75-Cent Face Mask". The New York Times. ISSN   0362-4331. Archived from the original on 25 March 2020. Retrieved 25 March 2020.
  11. "Pénurie de masques : une responsabilité partagée par les gouvernements" [Lack of masks: a responsibility shared by governments]. Public Senat (in French). 23 March 2020. Archived from the original on 9 April 2020. Retrieved 6 April 2020.
  12. Imperial College COVID-19 Response Team (16 March 2020). "Impact of non-pharmaceutical interventions (NPIs) to reduce COVID19 mortality and healthcare demand" (PDF). Archived (PDF) from the original on 16 March 2020. Retrieved 23 March 2020 via imperial.ac.uk.
  13. Dudley, Joshua. "Q&A: Dr. Rishi Desai Talks To Medical Professionals About What We Can Learn From COVID-19". Forbes. Archived from the original on 12 June 2020. Retrieved 18 June 2020.
  14. Stevens, Harry (14 March 2020). "These simulations show how to flatten the coronavirus growth curve". The Washington Post . Archived from the original on 30 March 2020. Retrieved 29 March 2020.
  15. Roberts, Siobhan (27 March 2020). "Flattening the Coronavirus Curve". The New York Times. ISSN   0362-4331. Archived from the original on 11 April 2020. Retrieved 12 April 2020.
  16. 1 2 Lopez, German (10 April 2020). "Why America is still failing on coronavirus testing". Vox.com . Archived from the original on 20 December 2020. Retrieved 12 April 2020.
  17. 1 2 3 4 Edlin, Aaron (March 2020). "Don't just flatten the curve: Raise the line" (PDF). p. 2. Archived (PDF) from the original on 18 April 2020. Retrieved 12 April 2020 via berkeley.edu.
  18. "We haven't failed on the virus". Australian Financial Review. 29 June 2021. Retrieved 2 July 2021.
  19. Scott, Dylan (31 December 2020). "Flattening the curve worked — until it didn't". Vox. Retrieved 2 July 2021.