U.S. stocks have been experiencing some of the most volatile trading in the past decade in recent weeks and that trend continued into Thursday morning as the three main stock-index futures contracts hit 5% limit-down rules for the second time this week.

Futures for the most-active Dow Jones Industrial Average US:YMH20 for March were down 5.22%, or 1,231 points, to 22,344 at their intrasession low Thursday, while S&P 500 futures US:ESH20 fell 5.08% to reach 2,601. Nasdaq-100 futures US:NQH20 declined 5.02% to 7,601.50.

Futures have plunged overnight setting up for another ugly decline for stocks Thursday, after President Donald Trump’s address to the nation Wednesday night at 9 p.m. Eastern, where he announced a month long ban on travel from Europe to the U.S. for foreign nationals, but failed to assuage fears about the spread of COVID-19, the infectious disease that has infected nearly 128,000 people, including recently celebrities like actor Tom Hanks and his wife Rita Wilson.

The U.S. stock futures volatility limit, which was also hit on Monday, is triggered when stock-index futures see a 5% swing in either direction during premarket or after-hours trading, outside U.S.’s 9:30 a.m. Eastern Time to 4 p.m. New York Stock Exchange trading period, according to the CME Group’s website.

When stock futures hit such levels, known as “limit up and limit down,” they aren’t allowed to move any higher or lower. Equity-index futures have different rules than other futures contracts.

On Monday, stock-index futures hit the daily downside limit that pinned their declines at 5% ahead of a brutal selloff sparked by a punishing slide in crude-oil prices CL00, +0.02% and worries about the spread of COVID-19.

7%, 13%, and 20% swings for S&P 500

The S&P 500 index itself dropped 7% near the start of Monday’s trading. That fall triggered a separate circuit-breaker rule that pauses stock trading during regular session for 15 minutes.

If the S&P 500 index SPX, -1.11% were to fall 13% on the day in the regular stock market session once trading resumes after a 7% halt, it would trigger another 15-minute halt. Trading wouldn’t stop if the decline occurred after 3:25 p.m. A 20% drop in the S&P 500 would trigger what’s known as a level three circuit breaker, which would stop trading for the remainder of the session.

Some experts say the unpredictable and violent moves in stock index benchmarks lately reflects a new regime of uncertainty fostered by the COVID-19 epidemic, the infectious disease that was first identified in Wuhan, China in December and has infected 115,000 and claimed more than 4,000 lives, according to data compiled by Johns Hopkins University.