The coronavirus infected the North American box office this weekend, as revenue is expected to sink below $55 million for the worst weekend performance in more than two decades. Even the September 11, 2001 terrorist attacks did not reduce audience turnout as badly.

In addition, more than 100 movie theaters in the U.S. have already shut down to respond to the crisis, including venues in New York, New Jersey, Pennsylvania and Washington state. Others have limited the capacity of auditoriums in response to the pandemic threat — further reducing potential grosses.

Exactly how far this weekend’s box office drops won’t be known until midday on Monday, but it is expected to be lower than the $59.7 million overall total scored on the weekend of Sept. 21, 2001. Numbers could fall as far as $54 million, which was how much was grossed on the weekend of January 14, 1998 — the previous record low. Comparing the box office landscape between then and now is virtually impossible given how much has changed in the theatrical market and because of the unprecedented nature of the coronavirus pandemic.

However, what is clear is that the past week of developments in the crisis, which have included a declaration of national emergency and multiple studios pulling their spring blockbusters from release, has cut box office grosses nearly in half as as numbers will drop at least 45% from the $100 million overall gross of last weekend, when Pixar’s “Onward” was released. That film, which opened to $40 million, has suffered a 74% drop to $10.5 million this weekend, the worst drop in Pixar history.

Also Read: 'Onward' Earns $10.5 Million in 2nd Weekend, Record 74% Drop as Coronavirus Hits Box Office

Like the spread of the virus, it will get worse for movie theaters before it gets better. Next weekend was supposed to bring the release of “A Quiet Place Part II,” and with it, a projected opening of at least $60 million. Paramount has removed the film from that date, while Disney has done the same for “Mulan” on March 27. With no new films and the public being urged to stay home to prevent spread of the disease, the box office will hit lows never seen in industry history.

That will leave theaters with hard decisions on whether to stay open. Thousands of theaters nationwide have reduced capacity in their auditoriums to provide space between moviegoers.

Cinemas in Europe have adopted similar policies; but in the past week, countries like France, Norway and Denmark have joined Italy in enforcing nationwide lockdowns, forcing theaters to close altogether. The same could happen in U.S. cities like New York and San Francisco, and perhaps elsewhere, if spread of the disease is not halted.