TRURO — Summer 2020 came and went with nearly the usual influx of tourists, many of them from metropolitan areas with far higher incidence of Covid-19. But the infection rate here has remained low. How did we do it?

In a typical summer, the population of the Cape more than doubles. In Truro, it grows from about 2,000 to more than 15,000; in Wellfleet, from some 3,000 to an estimated 17,000. And Provincetown, with just 2,800 permanent residents, swells to over 50,000.

Some of these summer residents are restaurant workers, often jammed in close quarters that are unhealthy even with no pandemic. Others are people here to party.

When summer began, Cape residents worried with good reason that visitors would infect our communities. There were tales, some apocryphal and some real, of hostile acts directed at cars with New York plates. The Truro Select Board and Board of Health even posted a (widely ignored) notice on the town website urging out-of-towners to stay away.

And yet, the Covid infection numbers scarcely budged. While Hyannis had it much worse, the Outer Cape seems to have escaped almost unscathed.

According to the official statistics in the state’s epidemiological database, which some wag named MAVEN (MAss. Virtual Epidemiological Network), the total numbers of Covid cases since the pandemic began have been Eastham 14, Wellfleet 7, Truro 12, and Provincetown 28. The latest report from the state shows, in the previous 14 days, one new case in Wellfleet, one in Truro, and none in Provincetown.

Are these numbers too good to be true? The statistics code people by town of residence. So, the database may show just 12 cases among Truro residents since the pandemic started, but what about Truro visitors?

If someone tests positive at Outer Cape Health Services and is staying in Wellfleet, what good does it do for contact tracers to know that the person’s permanent residence is Needham, or, for that matter, Hoboken? And what about the visitor who spends a few days in Provincetown, catches Covid, and goes back to New Haven before even getting tested? What about the restaurant worker in Eastham whose home is in Barnstable?

More than a dozen interviews with town and county health officials, elected representatives, public health nurses, and local advocates provide persuasive evidence that the numbers are basically accurate. “It’s not an exact science,” said Deirdre Arvidson, the public health nurse for Barnstable County, “but we do learn of most of the cases.”

How the System Works

The state is the overall keeper of data. When someone tests positive, the clinic or doctor’s office reports that information both to the MAVEN database and to the local public health office at both the person’s permanent residence and local address.

Each of the Commonwealth’s 351 cities and towns has at least one public health nurse who is responsible for contact tracing. The state database initially lists the case by permanent residence, but those numbers get adjusted based on what local officials learn on the ground.

“We get notified by the state only of cases with Wellfleet addresses,” said Hillary Greenberg-Lemos, Wellfleet’s health agent. “But we do learn about other cases, either from doctors or from the people themselves. Sure, we’d like more comprehensive official numbers, but I don’t think we’re missing people.”

State Sen. Julian Cyr of Truro, who worked in public health for six years in Gov. Deval Patrick’s administration, said he was initially concerned that the numbers might not be accurate.

“It’s not airtight, but it’s less of a problem than I feared it would be,” Cyr said. “From an epidemiological perspective, there is enough interaction with locals. I think we’d be seeing a higher incidence if there were all these cases flying under the radar.”

In short, while the system is far from perfect, it’s good enough. But how did we dodge that bullet?

Behaving Responsibly

First, most summer activity in these parts is outdoors. It’s possible, but really hard, to transmit Covid on a bicycle, in a kayak, on the beach, or at a campsite or cookout. Merchants have mostly cooperated by keeping down the numbers of customers allowed in stores, requiring masks, and providing for deliveries or drop-offs at the door.

For the most part, businesses and ordinary people have been responsible about reporting cases. In late July, when a worker at Mac’s Shack in Wellfleet tested positive, owner Mac Hay worked with public health officials and put the information on his own website. There were no further cases at Mac’s. But there was no state or local mandate that the public be notified when a restaurant worker tested positive, as the Independent reported on Aug. 6.

Outer Cape people recognize that the low incidence of Covid cases here is something precious, and they want to keep it that way. The local citizens tend to behave responsibly. We worry that visitors are far less conscientious, but apparently most took their cue from the good conduct of the locals.

There are also some important civic groups working to make sure town officials do their jobs. In Wellfleet, five health professionals created the Wellfleet Well Line (508-514-1633) to help residents navigate the system, and as a citizen watchdog on government authorities.

In Provincetown, no stranger to pandemics, the local government set up a mandatory mask zone and created a “community ambassadors” program, with paid staffers handing out masks and explaining the rules. Retailers that once displayed “No shirt, no service” signs began posting “No mask, no service.”

“People get it, respect it, and practice it, whether they are local or visiting,” said Provincetown Health Director Morgan Clark. “One of the reasons people come here is that it is a safe place.”

In short, everything that we cherish about the Outer Cape worked to keep the incidence of Covid low. Visitors must have absorbed some of this.

Of course, we have no idea what the fall will bring. The outbreak of cases at universities shows that this is no time for complacency. As of Sept. 15, according to the New York Times, there were 86 reported cases at Boston College, 83 at Boston University, 43 at Harvard, and 33 at Northeastern. On Monday this week, Nantucket officials held an emergency meeting to deal with an outbreak of at least 77 active cases on the island, WCVB Boston reported.

We also got lucky. Chatham restaurant workers and Falmouth lifeguard parties spawned three small outbreaks. That could have been Provincetown, but it wasn’t.

Robert Kuttner is a founding co-editor of The American Prospect. He lives in Truro and Boston.