When the producers of a new Steven Soderbergh movie put out the word that they needed extras, no one was prepared for thousands of people showing up at Fort Mason Center on Jan. 29 for the casting call.

The film is called “Contagion.” News of a chance to be in a film with Matt Damon, Kate Winslet and Jude Law became epidemic. Then again, some people just need the money.

“It took me over 40 minutes to find a parking space because thousands of people were there,” said Shelley Castellano (not her real name as she asked for anonymity), who was among the throng of hopefuls. “The line went around the building five times.”

Castellano was about to leave but was told that members of the Screen Actor’s Extra Guild could make $135 for eight hours, and time-and-a-half after that. If you are nonunion, you get a flat rate of $64 for 14 hours work. You start at 4 a.m.

Thousands more queued up behind her while she stood in line, so Castellano decided to stay. She had arrived at Fort Mason at 2 p.m. and finally got into the building nearly four hours later.

“By that time I was shaking from the cold,” Castellano said. “They said I’d be notified in 5 to 10 days if I’m hired. I would not have waited in that line if my unemployment benefits were not running out in a week or if I were nonunion.”

It seems that Rich King Casting needs a flood of extras for the Warner Bros. production.

“Apparently, the production company wants to fill Candlestick Park and needs 10,000 extras,” Castellano remarked. “That’s something I did not know. In my opinion, they are waiting to see how many SAG folks apply before notifying them, and will use the minimum number of union folks as possible.”

The large-scale scenes may explain why the casting call was publicized on TV, radio and Craigslist. Casting also took place on Jan. 30 at the Embarcadero YMCA. Shooting begins on Feb. 9.

They don’t call them cattle calls for nothing.