Production on Warner Bros. TV's The Flash has been halted due to the risks associated with the COVID-19/Coronavirus pandemic. Earlier this week, The CW stopped production on Riverdale because someone directly involved with the production had contracted the virus -- but this appears to be preventative, with no report of anybody on The Flash personally impacted and more a sense that large gatherings (as are necessary to run a big-budget series like The Flash, when you consider all the cast, crew, and others involved) are wise to stay away from. It is also likely that The Flash and other series are having difficulty with the travel involved for planned guest stars.
Given that this closure seems preventative, and that Berlanti Productions also operate the sets for CW shows like Supergirl and Batwoman, it seems likely that a number of fan-favorite series will be going into hiatus mode for the time being. There has been no official word from The CW yet.
The Flash unit manager Brent Crowell announced the shutdown "until further notice" in a note to cast and crew, according to Deadline, who reported that the closure is effective today, March 13, and that the cast and crew were advised not to report to work.
The COVID-19 outbreak has led to a string of cancellations and postponements across the entertainment industry, including Emerald City Comic Con, South by Southwest, Coachella, and WonderCon. These decisions come after the Centers for Disease Control and Prevention have issued guidelines recommending that people stay away form large gatherings in order to prevent spread of the virus, and the World Health Organization has officially designated COVID-19 as a pandemic. US President Donald Trump has also significantly limited travel from outside the country, and a number of major corporations are offering or sometimes mandating that employees telecommute rather than coming into the office.
Film and TV productions have also been hit hard, with Falcon and Winter Soldier suspending production too. It makes sense, when you consider that a major TV production involves dozens of people or more, including makeup and wardrobe workers who find themselves in close physical proximity with actors. During an outbreak where the CDC is telling people not to touch their face, it's hard to imagine anything that flies in the face of that more than superhero shows where a lot of actors have to spend literal hours in the makeup chair.
For now, The Flash will air as scheduled, on Tuesday nights at 8 p.m. ET/PT on The CW.