The Broadway League has suspended all performances until April 12 (including Six, which was scheduled to open tonight). New York governor Andrew Cuomo has banned gatherings larger than 500 people.
Last week San Francisco mayor London Breed banned any gatherings of 50 or more people in city run buildings which forced the San Francisco Ballet and the San Francisco Symphony to cancel performances. This week she extended the ban to any gatherings with over 1000 people which meant the sit down production of Hamilton had to temporarily close. Harry Potter and the Cursed Child initially tried to get around the ban by saying they were going to reduce seating in the 1667 seat theater to exactly 1000 people. California governor Gavin Newsom announced a statewide ban on any gatherings with more than 250 people so the theater had to relent and temporarily close the show.
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