The novel coronavirus epidemic first recognized in Wuhan, China, has stirred reactions ranging from unstinting generosity to playing the blame game, and on to overt discrimination. One of the more palpable responses has been anxiety and fear. Such negative social responses have mounted in recent weeks, in part because this particular epidemic has been sparked by a previously unknown pathogen, SARS-CoV-2, which causes COVID-19.

But if we’ve just met this virus, the human responses to it are mostly old acquaintances. The most important response? Expert mercy. It stems from an alchemy that mixes compassionate fellow feeling with interventions that save the sick and slow down the spread.

For three decades, my colleagues and I have worked together to confront epidemics — AIDS, Ebola, cholera, and drug-resistant tuberculosis — and are working still with thousands of caregivers spread across Africa, Latin America, and the Caribbean. The world must wake up to the threat the coronavirus poses, and the possibilities for effective and humane action this pandemic presents.

In order most effectively to address the threat, we need to trace and to treat, and to do that we need to test.

In spite of the head start offered by China’s dramatic coronavirus response, it’s been frustratingly difficult to get tested for the virus in the United States and across vast swathes of a long-interconnected world. That has not been the case in South Korea, where drive-through testing is widely available, and where contact tracing permits more targeted testing that must guide a speedy and effective response.

Tracing and testing can lead not only to prompt isolation but also to faster initiation of the supportive and critical care that many vulnerable patients will require. Mortality rates in South Korea, which has a rapidly aging population, have been a small fraction of that registered around Wuhan — and across northern Italy. Without more testing, we can’t compare these varied outcomes to the ones coming into view in, say, the state of Washington.

Increasing access to free and convenient testing is key to contact tracing, which is how transmission chains are identified and broken. Widespread awareness of local transmission often sparks social distancing, which increases the chances of slowing down the epidemic. This in turn decreases the likelihood of swamping health systems with a sudden surge in cases. From quarantine to social distancing, containment measures are not possible without robust social support for families obliged to work and study from home.

To be effective, outbreak responses must be merciful and humane, too. People must have food, supplies, safe shelter, of course, but also help with home-bound children as well as paid sick leave. Social support includes safe and rapid transportation to hospitals for the critically ill, since COVID-19 can be a disease with a stormy and unpredictable course. Strong social support, including the assurance that one’s loved ones will have access to quality care if they do fall ill, is the secret sauce of effective outbreak control. We learned during the West African Ebola outbreak that social distancing is almost impossible in settings of food insecurity or crowded slums and little in the way of help with caregiving and safe burials.

We need to protect health care workers.

During that epidemic, we also learned — or, rather, relearned — just how important this is. Sierra Leone, Guinea, and Liberia lost close to 1,000 nurses and doctors and other health care professionals, often because of a lack of widespread testing and of personal protective gear, quickly overwhelming and then shuttering the health care systems of all three countries.

In the absence of professional caregivers, family members fill in, but usually don’t have the necessary protective equipment. We need to prevent transmission inside hospitals and clinics while also avoiding the seduction of home-based care for the critically ill. Some of us will soon be gasping for breath — and unlikely to have oxygen canisters at home.

The quality of care — the expert mercy we need and expect in the face of serious illness or injury — is paramount.

People aren’t often lining up for testing in order to be isolated; they’re looking for expert mercy. What does that look like for those who fall ill with COVID-19? Sometimes it’s Meals on Wheels or a home-health aide with the right protective gear. When you’re dehydrated from fever and you can’t keep down fluids, it looks like IV fluids. When you’re quarantined with a mild case of COVID-19, such mercy may be dispensed at home, but when you’re critically ill, expert mercy looks like expert nursing care. When you’re coughing and short of breath, expert mercy is an oxygen mask or a mechanical ventilator.

Much of this care requires hospital beds, and their availability varies substantially even within affluent countries. South Korea has 12.4 hospital beds for every 1,000 people; the United States, 2.8. If we’re short on ICU beds in the United States, what will that mean for such places as Haiti or Rwanda or Lesotho or Sierra Leone?

We need to learn more about COVID-19 and about our varied social responses to it.

Folks are tired of hearing medical experts saying there’s a lot we don’t know. Is the virus seasonal? Why are many children spared? Why has mortality varied so widely from place to place? Do some genetic mutations account for variation in virulence and transmissibility or is that better explained by variation in the nature and quality of human responses? Does a positive test weeks after a negative one suggest reinfection or a stuttering recovery?

All this will be sorted out, as will questions about effective antiviral treatments and vaccines. But there are some things we do know. The social responses we’re seeing now have all been registered in previous epidemics. We know strong health care systems can help manage the surge by slowing the pace at which we need beds and, more important, nursing care. We know that expert mercy, and the sentiment of fellow feeling that underpins it, will be sorely needed in the weeks to come.

Effective containment efforts always turn, sooner or later, to an appreciation of these facts. When disease control and good care are two sides of the same coin, public support for necessary containment efforts rises. Social cohesion can be one result of catastrophe. Whether or not it’s displaced by blame, accusation, and stigma depend in part on striking the right balance between concern and resolve — and on avoiding panic, politicization, and polarization.