Data suggest Californians keep distance on holidays

Data suggest Californians keep distance on holidays

With another holiday weekend upon us, public health officials are once again wagging their fingers, warning Californians to heed social-distancing mandates against going out and gathering among family and friends.

But are lots of Californians really going out socializing on holiday weekends and fueling spread of the coronavirus?

Turns out, we may not be so bad after all.

At least by one measure — anonymized cell phone and vehicle tracking that data researchers analyze to indicate people’s mobility — it does not appear social distancing drops dramatically on holidays.

SANTA CLARA, CALIFORNIA – AUGUST 31: Customers walk past social distance signs on the floor in Westfield Valley Fair mall in Santa Clara, Calif., on Monday, August 31, 2020. (Nhat V. Meyer/Bay Area News Group) 

The interactive University of Maryland COVID-19 Impact Analysis Platform, which includes a social distancing index based on travel patterns derived from phone and vehicle data, indicates during the 15 days around Fourth of July from June 25-July 9, Californians were most mobile on July 3 — the Thursday before the holiday weekend.

But a higher percentage of people stayed home on July 4 and 5, said said Aref Darzi, assistant research scientist at the University of Maryland Maryland Transportation Institute.

That, Darzi added, “shows a consistent trend with the overall weekend trend observed.”

Concerned about hordes of cooped-up Californians flocking to beaches and parks, Gov. Gavin Newsom had pleaded with residents to avoid leisure trips and backyard barbecues to prevent them from unwittingly spreading the virus.

Others who analyze such mobility data made similar observations about our restraint. TOP Data analyzes cell phone location data to determine the number of daily close human interactions that last longer than 5 minutes.

“It appears that there isn’t an increase in the number of interactions on the holidays,” said Sean Lansing, director of client strategy at TOP Data. “The data shows that the number of interactions on holidays are consistent with the trend of interactions on the days leading up to the holiday and after the holiday.”

Can this really be? Doctors insist they see cases rise after holiday weekend gatherings.

“There’s a pretty tight correlation between known holidays and cases and hospitalizations,” said Dr. George Rutherford at the University of California-San Francisco.

New infections typically would appear within a week or two of the holiday weekend, as the maximum incubation period for a COVID-19 infection is 14 days.

SAN FRANCISCO, CA.- MAY 21: A late afternoon crowd of sunbathers enjoys the spring weather in Dolores Park from within the safety of their socially-distanced circles in San Francisco, Calif., on Thursday, May 21, 2020. (Karl Mondon/Bay Area News Group) 

California did see cases increase after major holidays earlier this year, though the numbers of new cases fluctuate day to day and the trend lines were generally increasing at the time anyway.

California, which reported 1,259 daily new cases on Mother’s Day, saw that figure peak over the next two weeks at 2,262 on May 19. The state reported 2,175 new cases on Memorial Day, which peaked over the following two weeks at 3,705 on May 30. And the state reported 8,597 cases July 4, a figure that peaked over the next two weeks at 11,694 on July 7.

“We have seen after major holidays such as Memorial Day and Fourth of July spikes or increases in cases, and that was both here locally and also nationwide,” said Santa Clara County Deputy Health Officer Dr. George Han. “We’re concerned the same thing can occur over the Labor Day weekend.”

So why the disconnect with the mobility data?

The University of Maryland’s Darzi noted that their mobility data do not take into account things like mask wearing and hand-washing, measures also believed to play prominent roles in the virus’ transmission.

Han said patients who have been infected after gatherings have admitted they didn’t always do that.

“When we talk to people who got infected, they say they let their guard down,” Han said. “They weren’t wearing masks, weren’t staying inside, weren’t socially distancing.”

Rutherford suggested that the people among whom the virus already is circulating significantly, such as those who live in close quarters and work in essential jobs, may also be the ones mostly gathering on the weekends, which would amplify its spread.

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