When it comes to COVID-19, what happens in Vegas doesn’t stay in Vegas.

Las Vegas casinos reopened June 4, and they have become a likely hotbed for the spread of the novel coronavirus, public health experts said. But if tourists return home and then test positive for COVID-19, the limitations of contact tracing in the midst of a pandemic make it unlikely such an outbreak would be identified.

Contact tracing, one of the pillars of stopping the pandemic, is a labor-intensive process where a health official tracks down anyone who’s been in contact with an infected person and takes steps to prevent the disease’s spread. But there is no national system in place for contact tracing, said Joshua Michaud, an epidemiologist and associate director of global health policy for the Kaiser Family Foundation. It’s decentralized and performed by local health agencies that may not communicate with one another, especially given their caseloads. So, if a casino had a “cluster outbreak” or “superspreading event” among visitors, it’s unlikely contact tracing would catch it, Michaud said.

“The way it’s set up right now, contact tracers are not looking for clusters that might identify outbreaks tied to traveling to a casino or other specific locations,” Michaud said. “You’re not actively looking for it, so you might miss that event. Contact tracing is not set up to answer those questions, so you’ll still be in the dark.”

A new analysis of smartphone data, conducted at ProPublica’s request, shows how interconnected the country is with visitors to Las Vegas — which heightens concerns about the limitations of interstate contact tracing. The companies X-Mode and Tectonix analyzed travel to and from Las Vegas during four days, a Friday to Monday, in mid-July. In compliance with privacy laws, X-Mode collects data from smartphone users, mainly those using fitness and weather apps that track their location. The data represents about 5% of the smartphone users in the United States. Tectonix analyzed the data and visualized it on a map.

During the four-day period, about 26,000 devices were identified on the Las Vegas Strip. Some of those same smartphones also showed up in every state on the mainland except Maine in those same four days. About 3,700 of the devices were spotted in Southern California in the same four days; about 2,700 in Arizona, with 740 in Phoenix; around 1,000 in Texas; more than 800 in Milwaukee, Detroit, Chicago and Cleveland; and more than 100 in the New York area.

The cellphone analysis highlights a reason the virus keeps spreading, said Oscar Alleyne, an epidemiologist and chief program officer with the National Association of County and City Health Officials. “People have been highly mobile, and as a result, it makes sense why we see the continuation of the surge.”

Typically public health agencies talk to one another at the state level, said Kimberly Hertin, disease surveillance supervisor in the Office of Epidemiology and Disease Surveillance for the Southern Nevada Health District, which includes Las Vegas in its territory. During the pandemic, local agencies have reached out directly to one another, she said, but the data isn’t tracked in a way that can show how often that happens with visitors to the Las Vegas resorts.

COVID-19 has made it impossible to get a complete picture in real time, she said. In the five weeks after Las Vegas reopened, the number of daily COVID-19 cases rose tenfold. Clark County has now had more than 50,000 cases. The number of new cases per day has declined since then, but the tally in Clark County, where Las Vegas is located, remains high enough that the Harvard Global Health Institute recommends stay-at-home orders. (There are no such orders in place.)

Hertin said the virus presents an overwhelming contact tracing challenge. Its incubation period is up to two weeks, so by the time it’s discovered in a tourist who came to Las Vegas, the person would probably be home. It’s “pretty much impossible” to identify the source of the cases, Hertin said.

Contact tracing efforts are focused on the person with a confirmed case to make sure they don’t spread it to others, not identifying the source of that person’s infection, Hertin said. “Once you’ve reached the point of community spread with this virus, it’s hard to jump to that conclusion of any clusters or outbreaks,” she said.

Beyond that, with the numbers as high as they are, local health departments can barely keep up with cases of people who live in their jurisdiction. “Our systems are in place for doing this when diseases are not highly prevalent,” like an E. coli or salmonella outbreak traced to lettuce or onions, Alleyne said. But COVID-19 is affecting hundreds of thousands of people, he said. “That magnifies and overwhelms the system.”

Public health experts say there are several keys to containing COVID-19: social distancing and wearing masks around others, having abundant and timely testing to see who has the virus, contract tracing to encourage those who had contact with infected people to isolate, and isolation for those infected. Reducing unnecessary travel and outings also helps stifle the virus.

In some cases, casinos say they are doing their part to identify situations in which their guests may have been infected during their stays. MGM Resorts International, which owns the Bellagio, Aria, Mandalay Bay and other properties, says in its safety plan that guests should email the company if they test positive.

MGM provided ProPublica with a statement about its safety efforts. But the company would not share how many times it has received emails. MGM also declined to say how many times it had notified the Southern Nevada Health District about possible transmission of COVID-19 on one of its properties.

MGM’s policy of having guests email the company and then referring them to the health district is “a lot of steps in a chain where you could miss a connection,” Michaud said. “If someone gets tested when they get back home and don’t email them back, it’s a piece of information they would never get.”

Hertin said the Southern Nevada Health District has received reports from the casinos about cases. But the available data doesn’t allow for an easy way to show which resorts or how many cases, she said. That may be possible to say in retrospect after the virus has subsided, she said.

The number of visitors to Las Vegas has steadily increased since it reopened. Many drive from neighboring states, and more than a million passengers came through the airport in June, which is about a quarter as many as the same month in 2019. Air travel nationwide is down more, 80% in June compared with the previous year.

The cellphone data analysis shows how travel to Las Vegas could be fueling the pandemic, Alleyne said. “In this rush to reopen and reposition the economic activities, all we’ve been doing is spreading and amplifying the reach of this disease.”

“Gambling With Lives”

ProPublica spoke to six public health experts who called casinos a high-risk environment for COVID-19. They are indoors, potentially crowded and filled with people prone to taking risks. It’s almost certain, the experts said, that casinos are a feeding ground for COVID-19.

“There is a serious opportunity for spreading the virus, especially for people who are mildly sick or don’t know they’re sick,” said Crystal Watson, senior scholar at The Johns Hopkins Center for Health Security. Up to 40% of those infected with COVID-19 show no symptoms. “We’ve seen big outbreaks kicked off by these types of situations.”

Workers in Las Vegas worry about the spread of the virus, too. Ralph McIver calls the kitchen at Binion’s Café, where he works, a “melting pot” of employees. The café is located in Binion’s Gambling Hall on Fremont Street in downtown Las Vegas. During his shifts, McIver works “almost elbow-to-elbow” with two colleagues on the cook’s line, grilling up ham and eggs, Hangover Burgers and Cowboy Cheesesteak sandwiches. “It’s difficult to stay socially distanced,” he said.

McIver is diabetic, which puts him at higher risk of a severe case of COVID-19. He also lives near his elderly mother, who is also at high risk. Binion’s didn’t require employees to be tested for COVID-19 before returning to work, which made McIver uneasy. He would feel better if he and his colleagues had initial and follow-up tests, he said. The longer the pandemic goes on, the more worried he feels. “My concern has only gotten worse.”

Binion’s officials did not return requests for comment.

Nevada regulators set minimum standards for COVID-19 protections but allowed the casinos to choose many of their own safety measures — to the dismay of many workers. That’s not a surprise, because gaming companies have significant sway over policymakers in Nevada.

Las Vegas could almost be called a company town, and its economy depends on tourism — even in the pandemic. In a rambling and contentious interview with CNN’s Anderson Cooper during the shutdown, Las Vegas Mayor Carolyn Goodman advocated for reopening despite the virus and appeared to offer the city as a sort of “control group” in an experiment. “How do you know until we have a control group?” she asked. “We offered to be a control group.”

When it comes to regulation in Nevada, Michael Green, a historian at the University of Nevada, Las Vegas, put it this way: “The casino industry is the tail that wags the dog. It may also just be the dog.”

The casinos do operate in a much different way since the start of COVID-19. Capacity is limited. Workers are checked for symptoms every day. Slot machines and seats at gaming tables are spread apart. Plexiglas barriers separate dealers and players, and hand-washing and sanitizing stations are located throughout the properties.

But in other ways, the regulators allowed the casinos to take the same varied response to the coronavirus as has taken place from state to state. At first, guests were not required to wear masks, even when indoors, which is one of the main protections recommended by public health experts. After COVID-19 cases started rising, Gov. Steve Sisolak, a Democrat, ordered face coverings for everyone in public spaces, particularly indoors. He also ordered the closure of bars in certain counties, including Clark.

The companies’ reopening plans varied in significant ways. Wynn Resorts required every employee to be tested, for instance, but MGM did not. And the standards that have been set have been unevenly enforced, workers told ProPublica. They said that even now visitors can go without masks by saying they’re smoking or drinking.

The biggest push for improved safety has come from the workforce. Officials from Culinary Union, the largest union representing the hospitality employees in Las Vegas, said in the initial weeks after reopening, they documented scores of cases where guests did not wear masks or failed to stay distanced, or casinos ran out of hand sanitizer or protective equipment for workers. The union filed a lawsuit in late June against several properties, accusing them of failing to protect workers. It’s now been resolved, with the union and companies working together to pass legislation that was signed by the governor that establishes protections for workers, including standards for cleaning, social distancing and hand-washing; notification within 24 hours if they may have been exposed to the virus; and inspections to ensure compliance.

Workers have also questioned the casinos’ efforts at contact tracing. Jessica Bremer’s experience became part of Culinary Union’s now-resolved lawsuit. In mid-June, Bremer said she heard from colleagues — not her employer — that one of her co-workers at Guy Fieri’s Vegas Kitchen & Bar tested positive for COVID-19. Bremer, a specialty cook, said her employer, The LINQ, which is owned by Harrah’s, part of casino giant Caesars Entertainment, did not handle the situation in a way that she believed protected her and other workers.

Bremer showed up for her shift after hearing her colleague had tested positive. But she told her supervisors she didn’t feel comfortable working. Bremer, 35, suffers from multiple sclerosis, an autoimmune disease that makes her more susceptible to a severe case of COVID-19. According to the lawsuit, one supervisor told her she would “have to deal with it” and another told her she should continue working. The company’s security team was determining which employees could be at risk because of contact with the infected worker, she was told. That didn’t sit well with Bremer. “Security officers don’t have a medical degree,” Bremer said. “If someone is going to deem what’s safe and what’s not safe, it should be a medical professional or someone with COVID training.”

Even after finding out Bremer had been on a recent shift with the infected employee, the company told her and other colleagues to work that day, she said. The employees pushed back, and so many refused to come to work the next day they closed the restaurant for 10 days, she said. Employees were paid during the closure, she said.

Employees at other casinos made similar allegations in the lawsuit. ProPublica asked officials from Caesars about Bremer’s account of the restaurant closing. They declined to talk about what she said, but they provided a statement saying their properties, “have deployed an extensive contact tracing program that leverages our sophisticated surveillance, security, and Human Resources tools.” The properties have also put “extensive” safety precautions in place, the statement said, and employees who are at high risk or do not want to come back to work are allowed to defer their return.

A spokesperson from the Nevada Department of Health and Human Services said 337 non-Nevada residents tested positive for COVID-19 in the state in June and most of July. The state agency could identify 10 out-of-state residents who were believed to be infectious while visiting Nevada and who tested positive for COVID-19 when they returned home. Public health experts said those numbers fall far short of quantifying the problem. The state numbers are certainly a “significant undercount,” said Alleyne, the epidemiologist with the association of county and city health officials.

Reopening Las Vegas is “gambling with lives,” said Michelle Follette Turk, an occupational health historian at UNLV. The government gambled by letting the casino owners create their own health and safety plans and failing to require masks until after the COVID-19 numbers were rising, she said. “The employers are gambling with employee life because they want to make a profit,” Turk added. “But employees are gambling with their lives — they need a paycheck.”

A Forest Fire

Pinar Keskinocak, a Georgia Institute of Technology professor who specializes in infectious disease modeling, compared the COVID-19 cases coming out of Las Vegas to a forest fire. Imagine if a group of trees was on fire and then some of the flames jumped to another area, where they ignited other trees, she said. That’s the kind of spread that can occur nationwide because of people gathering in Las Vegas, she said.

The risk is much more significant than the risk posed by schools reopening, Keskinocak said. At schools, the same group of students and teachers interact with one another every day, and they’re likely to live in the same geographic area. So any infection transmission will be contained within the group and perhaps their families. But in a casino, people from all over the country gather, and they get together in new groups every day. Then they return to places all over the country. In this way, she said, Las Vegas “could significantly fuel the disease spread.”

Discrepancies in how policymakers protect the public magnify the problem, Keskinocak said. One county or state might have strict interventions, like sheltering in place, or mask wearing, but a neighboring area might not, she said. “It’s important to have a concerted effort nationwide,” Keskinocak said. “If you are doing these interventions in a haphazard way and not coordinating, then we make progress and we regress again.”

Michaud, the Kaiser Family Foundation epidemiologist, said there are countries that were able to suppress the virus early on, and now they are returning to almost normal. But that’s not what happened in the United States. So now policymakers are trying to strike a balance between preventing the spread of the virus and resuming normal activity. And in many locations, like Las Vegas, decision-makers have sided with opening the economy. “I don’t expect a major lockdown occurring anytime in the near future,” he said. “That means there’s likely to be continued transmission. It’s horrifying, but it’s true.”

Loyal visitors to Vegas say they will keep coming.

Michele Heil and her husband take three trips a year to Las Vegas, where they are regulars at El Cortez Hotel and Casino on Fremont Street. The couple lives in central Illinois, where Heil said she is a social worker who does health care administration. Their June trip was planned before the pandemic hit, and they had no concerns about going.

Things went smoothly. She said she was more worried about COVID-19 on the plane than in the casinos. Their temperature was taken when they entered each property, people stayed socially distanced and the cleaning crews were active. “Before we left we already had our next trip planned,” Heil said. “We’re going back in September.”