The influential international group released a new economic forecast warning of severe consequences if COVID-19 cases spike as countries ease lockdowns meant to control the deadly disease.

The OECD expects the world economy to shrink by 6 percent this year and then rebound by 5.2 percent next year if a second wave doesn’t materialize. But if more cases emerge and lockdowns return, economic output will plunge 7.6 percent this year and only recover 2.8 percent in 2021, the group said.

“Extraordinary policies will be needed to walk the tightrope towards recovery,” OECD chief economist Laurence Boone said in a statement. “Restarting economic activity while avoiding a second outbreak requires flexible and agile policymaking.”

Even the OECD’s best-case scenario is about twice as bad as recent projections from the International Monetary Fund, which predicted in April that the global economy would contract by 3 percent this year.

The OECD says the US’s gross domestic product — the value of all goods and services produced here — will plummet by 7.3 percent this year and grow 4.1 percent in 2021 without a second wave of the virus.

But this year’s contraction would balloon to 8.5 percent if the nation is hit by another round of infections, while next year’s growth would be just 1.9 percent, according to the forecast.

Efforts to contain the coronavirus effectively shut down broad swathes of the US economy this spring, leading to record job losses and a 4.8 percent drop in GDP for the first quarter.

The US added 2.5 million jobs in May as many states began to ease virus-related restrictions. But COVID-19 has also had a staggering human cost, killing more than 100,000 Americans and more than 400,000 people worldwide.