The World Health Organization has declared that the disease caused by the novel coronavirus, COVID-19, is a pandemic. In the United States there are now more than 1,000 people infected with the virus and 31 have died as of March 11. As we see this crisis continue to unfold, one thing is becoming clear: Universal health care is not just essential to our health and economic security; it is essential to our national security as well.

Those charged with defending our nation have long recognized that containing disease is at least as crucial as state-of-the-art weaponry. Famously, George Washington inoculated his troops against small pox during the Revolutionary War—a gamble that contributed to American independence. Congress’ first big health bill was the 1789 “Act for the Relief of Sick and Disabled Seamen,” which grew into the Marine Hospital Service. In addition to providing care to the Navy and Coast Guard, the Service was a precocious system of social insurance for private workers, financed by a tax on the monthly pay of merchant seamen. In time, the Service oversaw a vast system of marine hospitals, launched federal investments in health research, and spearheaded efforts “to prevent the introduction of contagious or infectious diseases into the United States” (as the Federal Quarantine Act of 1878 put). It would later become the U.S. Public Health Service.

Today, as Covid-19 spreads around the United States, George Washington’s focus on microbial threats to national security seems newly prescient. Experts tell us that the key to saving lives—within the armed service and outside it—is to flatten the growth curve of infections. That, in turn, requires those who are sick to be identified, tested, and isolated, so they cannot infect others. But as long as millions of Americans cannot afford to see a doctor or pay for a test, the virus is likely to be difficult to stop—and more people are likely to die. Indeed, far more American lives are at risk from Covid-19 than international terrorism. Congress’ in-house doctor told Capitol Hill staffers that he expects 70-150 million people in the U.S. to contract the virus. If correct, that would likely mean hundreds of thousands of deaths.

Militaries have always been at the forefront of efforts to monitor and improve population health—if, for no other reason, than they need a ready supply of healthy recruits and conscripts. David Lloyd George, the British prime minister who put in place the country’s first national insurance system in 1911, declared, “You cannot maintain an A-1 empire with a C-3 population.” In his fight for national health insurance in the late 1940s, President Harry Truman claimed as inspiration the poor health of American recruits during World War II. Truman’s fight would eventually lead to the passage of Medicare and Medicaid in 1965 (symbolically, Truman was the first enrollee in Medicare). But universal health insurance for service members had already been put in place under Truman’s successor, Dwight Eisenhower.

Now we face a familiar threat in a new form. Covid-19 is exposing the dangerously high costs of our incomplete safety net. When people lack adequate health insurance, they don’t go to the doctor unless and until they are very ill. If they do, they may be left with a hefty bill. A man who had recently returned from China who developed respiratory symptoms went to the hospital in Miami. It turned out he did not have Covid-19, but he later received a bill for over $3,000 for uncovered expenses from his insurance company. A Brooklyn public school teacher went to the hospital with respiratory symptoms after returning from Italy. She was not tested for Covid-19 because she did not fit the testing criteria at the time, but she still received a bill for more than $10,000.

A number of insurers and states have since announced plans to waive copays and other costs for testing, but it’s still not clear that the uninsured will be covered. This uncertainty and inequality mean not only that those with no insurance or inadequate coverage will be stuck with a big bill. It also means that too many of those with symptoms or who’ve come into contact with likely carriers may not go to the doctor or hospital for fear of the cost. This is not just true when dealing with Covid-19. In a globally interlinked (and warming) planet in which new viruses and antibiotic-resistant infections can spread quickly, we need everyone covered for a wide range of health threats, with a particular focus on free preventive care.

The spread of the virus is already affecting military readiness. Two weeks ago, South Korea and the United States postponed annual joint drills after one American service member in South Korea and twenty two South Korean soldiers tested positive for the virus. The military has since canceled or scaled down exercises in Israel, Tunisia, and Morocco. On March 7, the Defense Department reported that a marine stationed in Virginia tested positive for Covid-19 after returning from overseas travel. On March 8, the Pentagon issued guidelines encouraging telework and other “social distancing” measures to reduce and prevent coronavirus transmission. Meanwhile, Lt. Gen. Christopher Cavoli, who leads the Army component of U.S. European Command in Germany, and some of his staff were forced to begin working remotely after learning they may have been exposed to the virus.

The issue isn’t just coverage; it is also costs. The more widespread the virus becomes, the more free testing could help us battle the virus. And when a vaccine becomes available, it should be available to everyone at little or no expense. (Alex Azar, President Trump’s secretary of health and human services, testified at a public hearing that the administration could not guarantee that a vaccine would be free when it is developed, despite the enormous government investment that will have to be made.)

Costs also matter because American health spending is so high that it crowds out other vital public investments. Michael Morell—the former CIA deputy director and acting director under both Republican and Democratic presidents—has warned that the rising costs of “entitlements” threatens “spending on defense, intelligence, diplomacy and foreign aid that we need to protect the country.” The problem, however, isn’t really “entitlements” like Social Security. It is health care costs that are rising far faster than our overall economy, driving up state and federal spending on Medicare and Medicaid. Every other rich democracy has figured out that you need to universalize coverage to have the capacity to restrain prices systemwide, which is why they spend so much less than we do on health care.

More broadly, we are being reminded that rationing access to critical health care resources on the basis of ability to pay is not just unjust, but also bad for public health. For a range of basic services, as well as critical ICU resources necessary to save lives, access should be based on individual need and the potential for positive spillovers, not whether someone has gold-plated private insurance.

Fortunately, the group most at risk—older Americans, and especially those with chronic conditions—already has public coverage through Medicare. It is high time this kind of publicly guaranteed coverage should be extended to all Americans, regardless of age or income. (One of us has argued that this could and should be done by expanding Medicare itself.)

Covid-19 is making painfully clear the connection between public health and national security. In doing so, it is providing yet another compelling reason to support universal health insurance.

Image: An ambulance drives by Brigham and Women’s Hospital, part of it will be a coronavirus, COVID-19, testing site, in Boston, Massachusetts on March 7, 2020. Photo by JOSEPH PREZIOSO/AFP via Getty Images