J. Stephen Morrison and Anna Carroll. "Which Covid-19 Future Will We Choose?." CSIS Commission on Strengthening America's Health Security, Center for Strategic and International Studies, April 01, 2020. Accessed January 25, 2021.

The Covid-19 pandemic will change history, but its path is not yet clear. This commentary summarizes the major drivers behind the pandemic—both natural and political—and sketches three possible scenarios for how the Covid-19 pandemic may play out.

Photo Credit: PAVEL GOLOVKIN/POOL/AFP via Getty Images

WASHINGTON, DC - MARCH 12: The Rotunda at the U.S. Capitol is empty after the last tour group has passed through March 12, 2020 on Capitol Hill in Washington, DC.
WASHINGTON, DC - MARCH 12: The Rotunda at the U.S. Capitol is empty after the last tour group has passed through March 12, 2020 on Capitol Hill in Washington, DC. Alex Wong / Staff / Getty Images

Today, the entire world is consumed by the rapid spread of SARS-CoV-2, the virus that causes Covid-19. Several Asian countries, including China, Singapore, Taiwan, Hong Kong, and South Korea, are grappling with containment and mitigation on the tail end of their epidemiologic curves. In much of Europe and North America, countries are contending with accelerated outbreaks with rapid spikes in cases and deaths. Many countries, including the United States, remain several painful weeks away from their apex.

Amid this global health crisis, it is important to consider what a post-Covid-19 world might look like and what destructive paths the pandemic might take. This commentary is an initial effort to succinctly capture the major drivers behind the pandemic—both natural and political—and to sketch three possible, broad scenarios for how the pandemic may play out in the United States. Similar trajectories may unfold throughout North America and Europe.

This analysis focuses primarily on the health security dimensions of the Covid-19 pandemic rather than its economic dimensions. It builds off the ongoing, important work others have done in this area (including recent analysis by Ezekiel Emanuel, Scott Gottlieb, Nicholas Kristof, Tomas Pueyo, and Ed Yong), as well as the models recently released by the Institute for Health Metrics Evaluation, the Imperial College Covid-19 Response Team, and

The exceptional speed of transmission of the virus is now widely recognized. SARS-CoV-2 spreads primarily through respiratory droplets (e.g., coughing and sneezing), and can be transmitted by people who are infected but not yet showing symptoms. An infected American is understood to infect 2.5 persons on average (the reproductive rate, R0). In order to break transmission, that rate has to be suppressed to below 1.0 through aggressive social distancing, testing, contact tracing, isolation, and quarantine.

The case fatality rate of Covid-19—the percentage of infected persons who die —is widely understood to be far higher than seasonal influenza. Between 3-11 percent of the U.S. population gets sick from the flu each season and only 0.1 percent of those die. The coronavirus may infect 40-70 percent of the American population and is likely to have a fatality rate in the range of 1-2 percent. Out of control outbreaks in Italy and Spain are reaching fatality rates closer to 10 percent.

What Are the Major Drivers that Inform the Three Scenarios?

There are several unknowns that will influence the trajectory of the pandemic, and these major drivers fall into three categories: the virus itself, government tools, and technology. All are to varying degrees shrouded in uncertainty, both scientific and political.

The Virus Itself

A vital driver is the duration of Covid-19 immunity. This refers to the amount of time a person maintains immunity to SARS-CoV-2 after recovering from infection. At present, we know far too little in this area, as more longitudinal research is required. If theoretically, a person can maintain immunity for a prolonged period (e.g., 12-24 months) post-recovery, they could conceivably safely return to public spaces even as the virus continues to circulate. Eventually, populations could reach herd immunity, where a high enough percentage of the population is immune to the virus that it peters out as it becomes more and more difficult for the virus to find a susceptible host. Inversely, if immunity is very short-lived, a person who has been infected could soon become reinfected.

A second is seasonality. Coronaviruses tend to peak in winter months and wane in warmer, more humid weather. Two of the four coronaviruses that cause the common cold abate in warm weather, but SARS and MERS did not have seasonal variations. At this point, it is still unclear whether Covid-19 transmission will slow during the summer and fall of 2020. The high transmissibility and extreme speed of this virus mean it is very likely to circulate the globe quickly and unimpeded. But if we are lucky and SARS-CoV-2 proves to be seasonal, we could use that temporary pause to stockpile medical supplies and build up our testing and laboratory capacities, strengthening our defenses against the successive waves of Covid-19 (winter 2020-2021, winter 2021-2022).

A third is viral mutation. Experts believe that SARS-CoV-2 is relatively stable and less prone to regular and rapid mutations. However, much more research is required to confirm this. If true, this would mean that immunity could be more predictable and long-lasting.

As all viruses mutate to some degree, subsequent SARS-CoV-2 mutations could have several divergent outcomes. It might mutate and die out; this is what happened with SARS and MERS. It might mutate in response to effective therapeutics, making it more resistant and potentially more persistent and severe. Mutations could also shorten the duration of immunity, as is the case with seasonal influenza.

Government Tools

The first large set of government tools are non-pharmaceutical interventions (NPIs). These consist of social distancing measures, including school closures, telework requirements for all nonessential businesses, bans of gatherings of groups larger than 10, and “shelter-in-place” orders. These are the only existing mechanisms to stop the spread of the virus.

Currently, U.S. federal guidelines encourage that these measures be adopted through April 30, but the federal guidelines do not mandate a national and maximally aggressive lockdown across the country. The current reality is a patchwork of highly variable policies of varying degrees of intensity and flexibility across states, territories, and municipalities.

If social distancing measures were implemented with maximum aggressiveness for 8-10 weeks, as seen in China, they could significantly break transmission and slow the spread of the virus, buying the country time to stock hospitals with key medical supplies [e.g., personal protective equipment (PPE), ventilators, intensive care unit (ICU) beds]. This would prevent hospitals from becoming overwhelmed, which would improve health outcomes and lower fatality rates, ultimately flattening the curve and extending the timeline for the outbreak. This would require an unprecedented level of coercion that would likely stir opposition.

The second set of tools relates to testing capacity. Singapore, South Korea, Taiwan, and Hong Kong have managed to control their epidemics through early and highly aggressive testing, contact tracing, isolation, and quarantine—without imposing harsh social distancing requirements. Improved and uniform testing capacity underpins every stage of Covid-19 response and recovery.

An ideal Covid-19 test would provide results in minutes, rather than days, and would minimize exposure to health care workers. In Denmark, the government plans to distribute self-test kits so that Danish citizens could determine infection status at home and only seek medical care in case of severe illness. In the United States, private companies are playing a more central role in developing new diagnostics; Abbott Laboratories is currently deploying a point-of-care test that can determine if a person is positive in just five minutes. Serological testing for antibodies is another critical tool that measures exposure and can be used to determine who within a given population has developed immunity to Covid-19, even without showing symptoms. Several countries, including China and Germany, have established immunity certification systems such that those who are proven to be immune can safely reenter a school system or a work setting.

Expanded testing capacity will need to be complemented by a national, digital disease surveillance system that can track testing and serological data both at the household level and at institutional interfaces where people are coming into contact in public spaces, such as transportation hubs, schools, and workplaces. This level of intensive monitoring of health conditions is expensive, involves more intrusion than Americans are accustomed to, and would raise questions of civil liberties and incite legal challenges.


Therapeutics are the first major category of technological drivers. Currently, a number of studies are underway to identify therapeutics that could lower Covid-19 mortality rates and accelerate recovery. An effective therapy—a bridge before a vaccine becomes available—would improve health outcomes and could potentially mitigate the need for medical equipment such as ventilators and ICU beds, freeing these up for the most severe cases and generally lowering the burden on hospitals and health workers. It is possible that a safe and effective therapy could be developed within the next six months.

The most crucial technological factor is vaccine production. A safe and effective vaccine is the only intervention that can definitively end the coronavirus pandemic. The earliest a proven vaccine could be distributed is likely the fall of 2021, though recent reports suggest a vaccine might become available in early 2021. It is wholly possible, however, that it will take much longer than that—even 3, 5, or 10 years—to demonstrate both vaccine efficacy and safety. Aggressive efforts to expedite vaccine financing, manufacturing, and distribution could shorten the timeline for ending the pandemic.

Possible Scenarios

Scenario 1: Best Case – Rapid Recovery

In the next 2-3-month period, the United States implements highly aggressive national social distancing measures and the nationally coordinated delivery of key medical supplies to major hot spots. Testing is widely expanded, allowing for more targeted, localized responses and the gradual easing of extreme social distancing throughout the country following the initial 2-3-month period of intense restrictions. Major urban centers do not become wildfires.

Seasonality provides a reprieve in the summers of 2020 and beyond, during which health systems can recover and prepare for subsequent waves. Therapeutics that successfully treat Covid-19 are discovered and scaled such that the burden of Covid-19 patients on the health care system is lowered substantially, increasing survival rates and ameliorating illness. Following the most severe, first wave of the virus (winter and spring 2020), total deaths in the United States do not exceed 240,000.

Covid-19 immunity lasts a long time, slowing the spread of the virus, and widespread accelerated serological antibody testing allows for those who are immune to return to work, potentially alongside low-risk populations (e.g., children returning to schools).

The economic stimulus packages succeed in keeping the U.S. economy warm, enabling a rapid economic recovery when the epidemic subsides and helping to maintain social stability throughout. The United States opens up its borders and resumes trade and travel with much of the rest of the world while closely managing the flow of migrants from areas that remain deeply impacted.

Impacted areas of Asia and Europe recover in tandem with the United States. Africa and many vulnerable low- and middle-income countries struggle with the pandemic, but the continued spread from those countries is manageable until a vaccine arrives.

The world rapidly produces and equitably distributes a safe and effective vaccine in 2021, early enough to partially staunch the second wave of the outbreak (winter 2020-2021) and more fully combat the third wave (winter 2021-2022). That progress further reduces the risk of reimportation of the virus from other countries.

The virus mutates and fizzles out, and eventually, the Covid-19 threat subsides completely.

Scenario 2: Mixed Case – Roller Coaster

In the spring of 2020, six weeks of a fragmented, chaotic federal response—no national lockdown, no national coordination of critical medical supplies, and no national testing system—squanders valuable time, opening the way for multiple wildfire outbreaks in urban centers throughout the country (e.g., Detroit, New Orleans, Chicago, Miami, Boston, Washington D.C., Dallas, and Atlanta). Delayed implementation combined with the premature relaxation of social distancing measures to reignite outbreaks across the country, resulting in a stop-go-stop-go, roller coaster pattern.

The lag in the provision of PPE to hot spots throughout the United States leaves medical workers vulnerable, causing a rise of infections and deaths among health care workers, further straining health systems and compromising the response. The rapid rise in cases temporarily overwhelms hospitals in major urban hot spots, leading to a significant spike in deaths throughout the spring and summer of 2020.

The total number of Covid-19 deaths in the United States range between 500,000 and 1 million.

Following this mid-2020 shock, a very late national lockdown is attempted, combined with efforts to nationally coordinate the delivery of critical medical supplies and to accelerate testing and contact tracing on a national scale. The seasonal drop in cases is marginal in the summer of 2020, providing little reprieve.

By winter 2020-2021, the United States slowly recovers and is able to “flatten the curve,” but only after protracted months of high death rates and multiple delays and false stops. Efforts to regain control over large urban wildfires are slow to achieve success.

Intense social distancing is ultimately required for months rather than weeks. Efforts to ease these measures often backfire, requiring a repeated retightening during the second wave (winter 2020-2021). That pattern, in turn, sustains the national economic crisis. The delayed deployment of a national testing system means that serological tests do not become available until late in 2020, and only then can those who are proven to be immune begin reentering the workforce.

Accelerated outbreaks persist in Europe and among low- and middle-income countries. The U.S. government is forced to be highly selective in the reopening of its border and reinitiation of travel and trade.

Additional emergency economic funding measures are passed, but economic fatigue intensifies, and these packages show diminishing returns. The federal government is forced to play a larger role, assuming ownership over wide swaths of the economy. As economic dislocation worsens, social unrest and violent instability rise.

Efforts to develop effective therapies take longer than hoped, with the result that antimalarials and plasma transfusions are not available to most of the country until the second wave (winter 2020-2021). A safe and effective vaccine is only available in time for the third wave (winter 2021-2022).

Scenario 3: Worst Case – Decline and Catastrophe

Social distancing measures are implemented and enforced in a fragmented, ineffectual manner across the United States. The federal government fails altogether to deploy a national testing and contact tracing system and to coordinate the delivery of critical medical supplies to the urban hot spots.

Chronic shortages of PPE persist as the pandemic worsens globally, causing demand to surge while supply remains low. This leads to exceptionally high, sustained infection and death rates among health care workers, imposing deep and lasting damage to the health system and crippling the national response for several months.

No effective therapies are discovered, health systems become overwhelmed as the virus continues to spread, and the supply of critical medical equipment (e.g., PPE, ventilators, and ICU beds) fails to keep up with demand. Overwhelmed hospitals fail, worsening health outcomes for both Covid-19 patients and for other hospital patients (e.g., heart attack, cancer, stroke, car accidents) and increasing death rates across the board.

The total number of Covid-19 deaths in the United States ranges between 1.5 and 2.2 million by the end of 2021.

Large segments of the world are unable to control the virus for extended periods, and the United States remains vulnerable to the reintroduction of the virus, forcing the U.S. government to keep its borders firmly shut and barriers to trade and travel high.

A safe and effective vaccine remains elusive, 5-10 years distant. Natural immunity does not last a long time, making those who recover susceptible to reinfection and impeding safe return to work and schools across large portions of the country. The stimulus packages are insufficient to avert deep and lasting damage to the economy. Entire sectors of the U.S. economy are nationalized.

As death rates rise and the economic crisis deepens, widespread, violent disorder intensifies, requiring a significant deployment of the U.S. military.

The Time to Act Is Now

Pandemics change history by transforming populations, states, societies, economies, norms, and governing structures. Political choices matter profoundly in determining outcomes. We know what is needed: Early, fast, aggressive action. A shutdown that is as universal as possible for four to eight weeks. A centralized command structure that rationalizes the marketplace and supports states in securing critical medical supplies. A national Covid-19 surveillance system that coordinates expansive testing and contact tracing at the local level. Investment in new therapeutics and vaccines. Economic measures that provide a social safety net. The time to act is now.

J. Stephen Morrison is senior vice president and director of the Global Health Policy Center at the Center for Strategic and International Studies (CSIS) in Washington, D.C. Anna Carroll is an associate fellow with the Global Health Policy Center.

This commentary is a product of the CSIS Commission on Strengthening America’s Health Security, generously supported by the Bill & Melinda Gates Foundation.

Commentary is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

© 2020 by the Center for Strategic and International Studies. All rights reserved.

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