WASHINGTON — Business economists expect the United States to suffer its worst downturn this year in more than seven decades before growth resumes sometime next year.

Overhanging that forecast, though, is the risk that a second wave of the coronavirus could threaten the economy once again.

A survey released Monday by the National Association for Business Economics predicts that the gross domestic product — the total value of goods and services produced in the United States — will fall 5.9 percent for 2020 as a result of the recession triggered by the virus.

The NABE panel of 48 forecasters expects the 5 percent annual GDP drop that occurred in the January-March quarter to be followed by a record 33.5 percent annual plunge in the current April-June quarter. Yet the NABE panel foresees economic growth returning in the second half of the year, with strong annual expansions of 9.1 percent in the July-September quarter and 6.8 percent in the October-December quarter.

In 2021, the panel forecasts GDP growth of 3.6 percent. But not until at least the second half of next year, according to an overwhelming majority of the forecasters, will the economy recover all its lost output from the recession. If a second eruption of viral infections were to occur, though, it would likely take much longer.