Facebook CEO Mark Zuckerberg warned Wednesday that reopening public spaces too soon “almost guarantees” continued coronavirus outbreaks and economic fallout.

“While there are massive societal costs from the current shelter-in-place restrictions, I worry that reopening certain places too quickly before inaction rates have been reduced to very minimal levels will almost guarantee future outbreaks and worsen longer-term health and economic outcomes,” Zuckerberg said on the company’s first quarter earnings call.

“The impact on our business has been significant, and I remain very concerned that this health emergency and therefore the economic fallout will last longer than people are currently anticipating,” Zuckerberg added.

Zuckerberg’s comments come as some states mull whether to reopen businesses that the Covid-19 pandemic forced shut.

The Centers for Disease Control and Prevention and the White House have laid out guidelines for state officials to follow when deciding to reopen businesses, but said the decision is ultimately up the the states. A handful of states, including Georgia, South Carolina, Mississippi and Montana, have eased social distancing restrictions, with some allowing gyms, restaurants and retailers to reopen.

The United States has reported more than 1 million coronavirus cases and at least 58,968 deaths as of Wednesday, according to data compiled by Johns Hopkins University.