More than 13 million cases of the coronavirus have now been reported in the United States, with the most recent million added within the past week, according to data compiled by Johns Hopkins University.

Johns Hopkins’ coronavirus tracker topped 13 million Friday afternoon. It previously reached 12 million Saturday, 11 million cases on Nov. 15 and 10 million cases on Nov. 9.

This new number comes just one day after historically scaled-back Thanksgiving for Americans transformed by the coronavirus pandemic. Warnings from health professionals pleading for a virtual Thanksgiving dulled traditional holiday activities.

The traditional Macy’s parade was limited to a television-only event and many families resigned to meeting on video for their turkey dinner. On Friday, masked shoppers turned up in smaller numbers at major retailers across the country on Black Friday as early online deals and worry about the spike in COVID-19 cases dulled enthusiasm for trips to the mall.

But experts say the coronavirus testing numbers that have guided much of the nation’s response to the pandemic are likely to be erratic over the next week or so, as fewer people get tested during the Thanksgiving holiday weekend and testing sites observe shorter hours.

The result could be potential dips in reported infections that offer the illusion that the spread of the virus is easing when, in fact, the numbers say little about where the nation stands in fighting COVID-19. The number of Americans who have tested positive passed 13 million Friday, according to Johns Hopkins University.

“I just hope that people don’t misinterpret the numbers and think that there wasn’t a major surge as a result of Thanksgiving, and then end up making Christmas and Hanukkah and other travel plans,” said Dr. Leana Wen, a professor at George Washington University and an emergency physician.

A similar pattern unfolds on many weekends. Because some testing centers, labs and state offices are closed on Saturdays and Sundays, COVID case numbers often drop each Sunday and Monday, only to peak on Tuesday.

Dr. Mark Rupp, professor and chief of infectious diseases at the University of Nebraska Medical Center in Omaha, said the effect of Thanksgiving is likely to be a magnified version of the weekend figures. The Thursday holiday will exacerbate the record-keeping discrepancies over the long weekend, artificially depressing the reported numbers for four or five days before spiking as test results catch up.

Experts worry how people might interpret the situation after the long weekend, especially if it takes a few weeks for Thanksgiving exposures to show up in testing data.

Cities and states generally use hospitalization and intensive care numbers, which lag behind virus case reporting, to determine when to increase or ease public health restrictions and recommendations. But the public is more likely to look at testing numbers or case counts, which might be misleading, Wen said, and waiting until hospitals are overwhelmed is risky.

“Where we are now is a completely unsustainable place. I think it’s extremely frustrating to those of us in health care to see our calls are not being heeded,” Wen said. “And the level of alarm that we have is not reflected in individuals’ behavior.”

There have been more than 264,000 reported deaths in the United States according to Johns Hopkins. Globally there have been more than 61.4 million confirmed coronavirus cases and 1.44 million deaths associated with the virus.