Since stepping down as surgeon general in April of last year, Vivek Murthy has turned his attention to what he considers to be America’s fastest-growing public health crisis. No, it isn’t cardiovascular diseases or obesity or smoking or even the nation’s system of health-care delivery. Murthy is taking on a more unlikely cause: loneliness.

“During my years caring for patients, the most common pathology I saw was not heart disease or diabetes; it was loneliness,” Murthy wrote in the Harvard Business Review in 2017. “The elderly man who came to our hospital every few weeks seeking relief from chronic pain was also looking for human connection: He was lonely. The middle-aged woman battling advanced HIV who had no one to call to inform that she was sick: She was lonely too. I found that loneliness was often in the background of clinical illness, contributing to disease and making it harder for patients to cope and heal.” Loneliness, he wrote, is associated “with a greater risk of cardiovascular disease, dementia, depression and anxiety.”

Loneliness is a concept that’s been gaining attention of late. It’s been 18 years since Robert Putnam’s seminal book Bowling Alone chronicled America’s “declining social capital” and how individuals had become less and less inclined to join community organizations, civic groups and social clubs. The two intervening decades since then -- with the encroaching ubiquity of the internet, the advent of smartphones and the explosion of social media -- can make Putnam’s talk of bowling leagues and Kiwanis clubs seem quaint. Countless essays have decried the ways technology is fostering a culture of ever-increasing isolation.

But much of that discussion has centered around loneliness as a social problem. Today, an emerging consensus on loneliness suggests that it isn’t just bad for communities, it’s a legitimate public health threat. A groundbreaking 2010 study from Brigham Young University found that weak social connections can shorten a person’s life by 15 years -- roughly the same impact as smoking 15 cigarettes a day. Research presented at the American Psychological Association’s annual convention last year showed that greater social connection corresponds with a 50 percent decrease in the risk of early death. A related report, which analyzed 70 other studies representing some 3.4 million individuals in North America, Europe, Asia and Australia, found that social isolation or living alone can be more harmful to a person’s health than obesity. Loneliness isn’t just an undesirable way to live. It can kill you.

More than 42.6 million adults over age 45 suffer from chronic loneliness, according to an AARP survey. More than a quarter of the U.S. population now lives alone, and more than half the population is unmarried. Census data show a decline in both marriage rates and the number of children per household. “Just because you live alone or are unmarried, doesn’t mean you aren’t connected,” says Julianne Holt-Lunstad, a neuroscience professor at Brigham Young and the author of the 2010 study. “But each one of those things is robustly linked to risk. It’s like [body-mass index]: It’s crude and has its limitations, but it is a strong predictor of obesity risk.”

Governments in some countries have begun to take action. The United Kingdom launched a national campaign to fight loneliness in 2011, an effort that Australia emulated shortly thereafter. Denmark has introduced piecemeal efforts to address isolation, such as its “Danmark spiser sammen” (“Denmark eats together”) campaign to encourage everyone -- from government entities to nonprofits to private companies -- to host dinner parties. Earlier this year, British Prime Minister Theresa May announced that she would make loneliness a policy priority, and appointed a minister for loneliness, a new cabinet position in charge of creating new initiatives and shaping policy.

There haven’t been similar large-scale efforts in the United States to address the health impacts of social isolation. Most of the work that is being done to combat loneliness is happening on a hyperlocal level: YMCAs hosting social nights for seniors, for example, or animal rescue centers running cat foster care programs for homebound adults. But experts say a local approach might not be a bad place to start. “Social activism typically begins at the community level in America,” says Sachin Jain, president and CEO of CareMore, a health plan serving Medicaid and Medicare beneficiaries. In fact, Jain takes to task some of the high-profile efforts in other countries. A public awareness campaign, he says, doesn’t necessarily mean there’s a systematic plan to address policy in a meaningful way.

The CareMore health plan is in seven states. Last year, the group kicked off “Be in the Circle: Be Connected,” an initiative in four states to integrate social connectivity into the primary care setting. When seniors come in for primary care visits, they’re now asked several questions aimed at giving doctors a better sense of the patient’s potential for social isolation: How often do you see friends? How frequently do you go to the grocery store? If a senior is deemed to be at risk for social isolation, they can receive home visits and weekly phone calls from a social worker. Many lonely seniors’ only human interaction is when they visit their doctor’s office, so CareMore took advantage of that by redesigning their care centers to include more social activities such as Zumba classes and group lunches.

Jain says that some of the participating seniors will answer their weekly phone call by greeting their social worker by name, “because that person is the only one calling them.”

The largest advocacy organization for older Americans in the country is also mounting a campaign against loneliness. The AARP Foundation launched the Connect2Affect tool last year, an online assessment and portal that helps seniors figure out how isolated they might be, and connects them with resources in their ZIP code. Foundation President Lisa Marsh Ryerson says the effort is still in awareness-building mode, but collaborating with governments will be crucial. “For effective solutions, we will need public-private partnerships. When I think about working with governing bodies, I think about working with them on the decisions that are made around accessible transportation, walkable sidewalks,” things that can determine whether an older person is able to leave their house or not, Marsh Ryerson says.

In England, the plan for the minister for loneliness is to convene with leaders across industries -- from transportation to finance to health care -- to see how all roles of government can help get people more connected. One of the first orders of business is expanding the role of community connectors across the country. Similar to CareMore’s model, the community connector works as a liaison between a primary care physician and the patient. If someone is suffering from isolation, the community connector can help create a plan for them to feel more connected to other people. “One of the things that’s key about loneliness is it’s so individualized, not everyone needs the same amount of interaction,” says Kellie Payne, research and policy manager for England’s Campaign to End Loneliness. “The connector can help them understand what their personal needs are.”

As governments begin to think about this issue, they’ll be looking for policy solutions that can have a big impact. The interventions in England and for CareMore beneficiaries are not only relatively low-cost, they’re also scalable. Other initiatives to mitigate the risks of social isolation might not be as immediately obvious. For example, last year a bipartisan bill to make certain hearing aids available over the counter was signed into law by President Trump. That’s significant, experts say, because hearing loss is one of the key risk factors that causes some seniors to retreat away from others. “People will come to me and say, ‘What can we do to legislate good relationships?’ Well, we can legislate things that reduce risk,” says Brigham Young’s Holt-Lunstad. “That’s why I love the hearing aid example. No one’s freedom was impacted. We say we don’t really know what to do about [loneliness], but there are interventions that have worked.”

Advocates say that policy changes like that are a short-term goal. But the longer-term goal is for everyone to start looking at social interactions as an integral part of a person’s well-being, like eating well and getting enough sleep. “If we think about our checklist of being healthy, it usually includes exercise and eating vegetables and not smoking,” says Payne. “But we don’t think about our social connections as being just as vital as those things. If you have good contacts, the restorative effects can be just as strong as those other, more traditional methods of being healthy.”

As more American health plans move to a managed care system -- one that pays for services based on quality instead of quantity -- CareMore’s Jain says it’s imperative that social isolation be integrated into health care. “We’ve defined loneliness as a treatable human condition, and up until now there just haven’t been payment models to encourage that,” he says. “But primary care doctors now have an obligation to address it.”