WASHINGTON — A critical snapshot of the job market and the economy to be released Friday is expected to show a further deceleration in hiring as the nation’s viral caseload creeps higher and as government financial aid has faded.

When the Labor Department issues its September jobs report, economists predict it will show a gain of 850,000, according to a survey by data provider FactSet. That would mark a third straight monthly slowdown, after June’s 4.8 million job gain, July’s 1.7 million and August’s 1.4 million.

If the forecast for September proves accurate, it would mean that the economy has regained only slightly more than half the 22 million jobs that vanished when the pandemic flattened the economy in early spring. Should job gains continue to remain below 1 million a month, it would take until late 2021 or 2022 to recoup them all.

So far, hiring has rebounded quickly compared with previous recessions. The gains have mainly reflected millions of temporarily laid-off Americans who were called back to work when retailers, restaurants, medical offices and other businesses reopened, at least partly, from their pandemic-induced shutdowns.

But slowing job growth has raised the specter of a prolonged downturn that feeds on itself and becomes harder to fully reverse. Many temporary layoffs are becoming permanent as hotels, restaurants, airlines, retailers, entertainment venues and other employers anticipate a longer slump than they initially expected. There is also growing fear of a resurgence of the virus, which would compound the threat.

The longer that laid-off workers fail to find jobs, the more likely it is that they will have to look for new work with new employers or in different occupations. Doing so can require additional training or education and take much longer to achieve than just returning to a previous job. The