"We're going to have to face the harsh reality in some states that we may need to shut down again," said Dr. Jonathan Reiner, a professor at George Washington University School of Medicine.And the second wave of state shutdowns could be more damaging than the first.
"Because of quarantine fatigue, because of the economic effects of quarantine, another round of shutdowns might have even larger effects on businesses that may be on the edge of not being able to stay solvent," said Dr. Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington.The economic toll from one round of shutdowns has been staggering. More than 44 million people in the United States have filed for initial unemployment benefits since mid-March.But the pandemic is far from over. More than 115,000 Americans have died from coronavirus, and hundreds more are dying from the virus every day.
"Covid's not taking a summer vacation," said Dr. William Schaffner, an infectious diseases expert and professor at Vanderbilt University Medical Center.
"It's actually having new opportunities to spread."
Murray said the "biggest and most difficult choice" states could face in the coming months is managing a potential second shutdown.
And the consequences of another shutdown would be wide-ranging, US Treasury Secretary Steven Mnuchin said."We can't shut down the economy again," Mnuchin told CNBC. "I think we've learned that if you shut down the economy, you're going to create more damage. And not just economic damage, but ... medical problems and everything else that get put on hold."
But the federal government hasn't been in control of shutdowns and reopenings. Those have been at the discretion of each state.
"If you run out of hospital beds, and you run out of ICU beds ... (states would) have to shut down," said Reiner.
It's happened before
Second shutdowns aren't just possible -- they've already happened in some parts of the world during this pandemic.Hong Kong and Singapore seemed to have coronavirus under control and started easing restrictions -- only to have major resurgences that led to stricter rules.
Japan's second-largest island, Hokkaido, also shut down to control the spread of coronavirus. "But they opened too quickly," Reiner said, leading to a Covid-19 comeback.
"They shut down again. And that's how they extinguished the virus."
How Americans can prevent another round of shutdowns
While states try to revive the economy, the fate of this pandemic is largely up to individuals.
"People must observe the safety guidelines," top White House economic adviser Larry Kudlow said.
"Social distancing must be observed. Face coverings in key places must be observed."Wearing a face mask is critical to slowing the spread of coronavirus because of how easy it is to infect others -- even without any symptoms. "We've got to take action now so that we avoid a shutdown in the future," said Lina Hidalgo, the head of government in Harris County, Texas -- the third most populous county in the United States. Like many parts of the country, Harris County has seen surges in Covid-19 hospitalizations since Memorial Day weekend.
"That only continues to grow," Hidalgo said Friday.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said "the best thing to do is to avoid crowded areas."
"But if you're not going to do that," he said, "please wear a mask."
CNN's Amanda Watts contributed to this report.