The S&P 500 logged its worst day since February as a growing list of nations, including the United States, moved to prohibit travel from half a dozen or so African countries.
Friday’s decline pulled the benchmark S&P 500 down further from a record high reached just last week.
Mr. Lerner said a modest sell-off is hardly unexpected, given the heights at which stocks have been trading.
The drop comes just three days after the United States and five other countries announced a coordinated effort to tap into their national oil stockpiles, to try to drive down rising gas prices.
Brent futures, the European benchmark, fell 11 percent to about $73 a barrel.
Treasury plunged 15 basis points, or 0.15 percentage points, to 1.48 percent, the biggest single-day drop since March 2020.
In an echo of the market fluctuations of last year, stocks that flourished under lockdowns and quarantines rose, including Zoom and Peloton.
As several countries including Britain and France rushed to restrict flights from South Africa and seven other African nations, airline stocks dropped.