SAN FRANCISCO — Millions of Italians were allowed to return to work this week after nearly two months in lockdown because of the coronavirus. Children are free to play outside in Spain again after the pandemic kept them indoors for six weeks.

About half the states in the U.S. have taken similar steps to loosen the social distancing measures imposed to keep the virus from spreading, and others are considering it.

But whereas those two hard-hit European countries – second and third behind the U.S. in case totals – have considerably slowed their rate of infection and started to bend their respective curves, the trajectory of U.S. cases looks straight like an arrow shot into the sky, with no sign of its descent in sight.

The U.S. has had at least 20,000 cases of COVID-19 each day since mid-March, and a government projection raised that figure to 200,000 – with 3,000 daily deaths – by June 1, according to the New York Times.

The influential model from the University of Washington’s Institute for Health Metrics and Evaluation nearly doubled its national death projection Monday, from 72,000-plus to 134,475 by Aug. 4.

And a new model from the Wharton School at the University of Pennsylvania projects almost 117,000 deaths by June 30 – up from the current 71,000-plus – even without states reopening. If states fully reopened, the death toll would rise to a staggering 466,000 by the same date, the model predicts.

Except for notable outliers like New York state, the American pandemic epicenter that has shown a dramatic decrease in its daily cases over the last 10 days, the country in general seems to have plateaued. Only 12 states are currently showing a sustained case reduction, although some have had dwindling followed by a rise. Another 15 states have experienced sustained increases.

Still, with dire models and a curve that hasn’t bent, the U.S. is pushing toward reopening and to dissolve the task force that has headed up the federal government’s response to the pandemic. What happens next?

If coronavirus keeps spreading in US, blame 'inadequate social distancing'

Given the less-than-encouraging data, many experts ponder warily the consequences of much of the country reopening for business — even with some conditions.

“It's possible that this phenomenon reflects a recent ramp-up in testing rather than continued linear growth in cumulative infections,’’ Penn Wharton senior analyst John Ricco said of the U.S.’s inability to flatten the curve. “But as our analysis suggests, it's a real possibility that the virus’s (transmission rate) remains above 1 in many states, which would mean that the virus will continue to spread indefinitely. Inadequate social distancing — whether as a result of official restrictions or noncompliance — is likely to blame.”

Added fellow senior analyst Alex Arnon: “Distancing policies in general have been less strict and less strictly enforced in the U.S. than other hard-hit countries, though there are a lot of regional differences. There has also clearly been some partial reversal of social distancing in the second half of April. I can see it in the data and I can see it out my front window.’’

Predictive models have adjusted for the loosening of restrictions, some of it likely prompted by growing protests as the constraints have devastated the economy. The IHME model relies on cell phone data from four sources to track mobility, which institute director Chris Murray said increased even before states started reopening.

That was a major part of why death totals in the model skyrocketed, Murray said, adding that social distancing unquestionably works in curbing the virus’ spread.

“The challenge, of course, is there’s enormous economic turmoil created by that,’’ Murray said. “I think the premier discussion in terms of policy is what’s the right trade-off, and that’s where some of these models may be helpful in thinking that through.’’

The Penn Wharton one, for example, forecasts that by June 30 the gross national product would be 11.6% lower than one year earlier – and 18.6 million jobs would be lost in May and June – if states did not reopen before July.

If they fully reopened right away, the GDP on June 30 would increase by 1.5% relative to not reopening, and job losses in May and June would essentially be wiped out. A partial reopening would result in a 1% GDP increase year over year and 14 million job losses in those two months, but would cost an additional 45,000 lives, for a June 30 total of 162,000.

Coronavirus cases could spike if US isn't 'careful' with reopening plans

Dr. George Rutherford, head of infectious disease and global epidemiology at the University of California-San Francisco, points out the balancing act decision makers must perform does not automatically fall on the side of keeping people safe.

“There’s always a tension between the economy and sheltering in place,’’ he said. “Bad economies are as hurtful to health as viruses."

Rutherford has been put in charge of training the 10,000 contact tracers California Gov. Gavin Newsom wants to have in place as the state moves to its next phase in confronting the pandemic, with an emphasis on testing, tracing and isolating.

Because of its size and diversity of states and cultures, Rutherford said it’s not fair to compare how the U.S. has done in responding to the pandemic to much smaller countries. The strict measures implemented in Italy or someplace like the semiautonomous region of Hong Kong, where the government went as far as requiring those on home quarantine to wear monitoring bracelets, would likely prompt intense backlash in the U.S.

“There are 100 different epidemics in the United States, and you have to manage each one separately,’’ he said. “These kinds of big, broad sweeping policy declarations can be overly generalized. You want stuff that’s specific for your area.’’

Though some analysts believe the virus may recede in the heat of the summer, Rutherford is among those who expect cases to multiply quickly as people get complacent about mitigation and distancing.

Steven Gjerstad, presidential fellow in the Economic Science Institute at Chapman University in California, said it may be possible to increase economic activity while maintaining social distance. Online shopping is one example.

However, he warns against people letting their guard down, and notes that high temperatures did not keep the virus from resurging in Singapore.

If reopening is done carelessly, then the effect on case growth will show up with a lag: "The increased rate of new diagnosed cases will begin to show up about 10 to 12 days later,’’ Gjerstad said. “We all remember that diagnosed cases in the U.S. went from seven community transmitted cases on March 1 to 68,000 24 days later. That kind of growth can happen again if we aren’t careful about how we begin to reopen businesses.’’