Earlier this year, a novel influenza captured the world’s attention when what became known as “swine flu” or H1N1 (hemagglutinin type 1 and neuraminidase type 1) emerged in La Gloria, Mexico.

In February 2009, five-year-old Édgar Enrique Hernández suffered from a flu virus that had mutated from pigs. Edgar recovered, but the mutated virus gave rise to a global pandemic. Just five months after the first case, there were 300,000 laboratory confirmed cases, 4,000 deaths, and infections in 191 countries and territories.

Given the pace of infections, the World Health Organization declared a pandemic and many governments increased preparedness measures. Last week, President Obama declared it a national emergency. While we are all racing to get our vaccines, increasing our stocks of hand cleaner, and trying to avoid hand-shaking (this seems culturally impossible), it’s also good to take stock of how and why influenza became a security concern.

Fifteen years ago, military thinkers and policymakers were unlikely to link public health and international security. Instead, health issues were decidedly domestic issues and at odds with traditional foreign policy concerns such as potential peer competitors, nuclear proliferation, or rogue states. However, after the emergence of avian influenza in Asia in 1997, national security professionals began to reconsider infectious disease as a potential matter for international security. Interest heightened again during the 2003 Severe Acute Respiratory Syndrome (SARS) outbreak that infected 8,000 and killed 800 worldwide. Though these separate outbreaks were unrelated and relatively small, the potential for a pandemic is very real. The last three pandemics of the twentieth century killed over 43 million people.

In its 2007 report on future security challenges, the U.S. military noted that, “a pandemic in North America would be protracted and pervasive, causing substantial societal impact and persistent economic losses in almost every state.” This may be realized in 2009-10 Director-General of the World Health Organization, Dr. Margaret Chan reminded the world that “Pandemic influenza is … looming on the horizon. The threat has by no means receded and we would be very unwise to let down our guard, or slacken our preparedness measures. As with climate change, all countries will be affected, though in a far more rapid and sweeping way.”

In addition to pandemic influenza in the United States and Europe, national security professionals have consistently viewed public health as a security issue in developing countries. For example, in his 1996 national security strategy, President Clinton highlighted disease and its impact on development. “New diseases, such as AIDS, and other epidemics which can be spread through environmental degradation, threaten to overwhelm the health facilities of developing countries, disrupt societies and stop economic growth.” While there are strong humanitarian reasons to be concerned about disease in developing countries, by the end of the 20th century it was the wide-reaching threat of the effects of disease that became the focus of concern.  Accordingly, the United States began to articulate strategies that addressed disease as a material threat to Americans. The 1999 National Security Strategy noted, “diseases and health risks can no longer be viewed solely as a domestic concerns.” Instead, health is a matter of national security.

President Bush continued the tendency to view disease as an international security challenge in the twenty-first century and stated, “We will also continue to lead the world in efforts to reduce the terrible toll of HIV/AIDS and other infectious diseases.” White House concerns for health security continued under President Obama. He told the UN General Assembly, “far too many people in far too many places live through the daily crises that challenge our humanity – the despair of an empty stomach; the thirst brought on by dwindling water supplies; the injustice of a child dying from a treatable disease; or a mother losing her life as she gives birth.” Consequently, U.S. health assistance programs now exist in almost every country of the developing world.

Concerns about public health are not simply a Trojan horse for U.S. expansionism or hegemony, as some critics may warn (adding disease to the long list of irregular challenges is not in the Pentagon’s interests). Rather, the tendency to view disease as a national security threat is common to the foreign policies of virtually all developed countries.  These nations recognize that along with he benefits of globalization there are increased vulnerabilities as well.  For example, the Netherlands has defined its national security challenges through diverse threats such as SARs, bird flu, floods, and terrorism, acknowledging that through increased interdependencies, what once were relatively minor threats can lead to societal disruption.

Similar sentiments are conveyed in the United Kingdom’s national security policy, which sees pandemics as a part of threats and risks that “are driven by a diverse and interconnected set of underlying factors, including climate change, competition for energy, poverty and poor governance, demographic changes and globalization.” And the European Centre for Disease Prevention and Control noted, “Pandemics do not recognise [sic] national borders. They affect not only public health but also societies and economies throughout the EU and the world.” Transnational disease has the potential to slow the international movement of goods and people.

Pandemics, by their very nature, are international in scope and have become a key feature of the security landscape. Fortunately, pandemics do facilitate international cooperation since all people are vulnerable regardless of nationality, ideology, or geography. The United States and China are at the forefront of this and cooperate at bilateral, global and regional levels to prevent and respond to pandemic influenza. Ironically, whereas traditional security concerns like military modernization can cause friction between great powers, human security concerns can create trust.  And whereas fear can cause conflict, shared insecurity can generate peace.

Derek Reveron, an Atlantic Council contributing editor, is a professor of national security affairs at the U.S. Naval War College in Newport, Rhode Island.  These views are his own.