Users of the fitness tracking device Fitbit are moving a lot less, a sign that social distancing initiatives intended to slow the spread of the coronavirus are having an impact.
Steps by individual U.S. Fitbit users were down an average of 12% during the week of March 22 compared to the same period in 2019, according to a report from Fitbit on Tuesday. In certain large metropolitan areas, the decline was even sharper—likely because many workers are no longer commuting to the office and have reduced their more active lifestyles to comply with shelter-at-home orders. That includes San Francisco and New York, where steps were down an average of 20% for the week; Boston, where steps fell 17.5%; and Seattle, where they declined nearly 14%.
The greater inactivity was even more pronounced in some European countries that are under strict nationwide lockdowns. In the U.S., only certain states have issued shelter-at-home orders, meaning that residents in many places haven’t had to change their lifestyles much and are freer to walk or run.
In hard-hit Spain, for example, Fitbit users walked an average of 38% less than the same period last year. Meanwhile, in Italy, steps were down 25% and, in France, they were down 20%.
The data was gathered from the fitness tracking devices of more than 30 million Fitbit users globally. But the findings aren’t necessarily representative of the general population’s behavior in any particular country. Fitbit users may, for instance, be more affluent than average, more likely to be able to work from home, and more physically active than nonusers.
Fitbit’s data also shows that while the decline in U.S. activity has been lower than in some other countries, Americans were starting from a lower baseline. In the first three months of 2019, Fitbit users in Japan, China, Italy, Hong Kong, and Great Britain all averaged over 10,000 steps in most weeks. For Americans, the average was substantially lower at just over 8,000.
This relative inactivity may be cause for both optimism and worry as the virus makes its way across America.
On the one hand, some have argued that countries like Spain and Italy have been hit particularly hard by the virus because of normally vibrant public spaces, particularly in cities, enabling its early spread. Americans’ relatively sedentary lifestyles, and greater reliance on cars, may slow the pandemic’s progress by comparison.
On the other hand, the virus appears to be particularly lethal to those with certain underlying health conditions. Some of those, including obesity and diabetes, are strongly linked to a lack of physical activity. A lack of exercise has contributed to making America one of the most obese nations in the world, pointing to bleak consequences as coronavirus spreads.
More must-read tech coverage from Fortune:
—How the coronavirus stimulus package would change gig worker benefits
—Inside the global push to 3D-print masks and ventilator parts
—Apple focuses on what’s next amid coronavirus outbreak
—A startup is building computer chips using human neurons
—Listen to Leadership Next, a Fortune podcast examining the evolving role of CEO
—WATCH: Best earbuds in 2020: Apple AirPods Pro Vs. Sony WF-1000XM3
Catch up with Data Sheet, Fortune’s daily digest on the business of tech.