Steven Soderbergh’s movie “Contagion” manages to do for global pandemics what porn does for sex: makes it look phony. There are the requisite scenes of foaming corpses, dead monkeys, scientists looking with alarm at computer screens with rotating polyhedrons and pathologists in lab coats performing autopsies (in this case on Gwyneth Paltrow, alas) and saying things like: “Should I call someone?” “Call everyone!”

One should not joke about this.
Apparently we are only a bat-infecting-a-pig away from another virus along the lines of the Spanish Flu of 1918, which, one character ominously tells another, killed 1 percent of the population of the world. Viewers are also told that people touch their faces up to three thousand times a day.

Some of this is entertaining stuff, a lot of it is educational (supposedly Soderbergh engaged experts to assure authenticity) and some of it is scary. But it does not add up to a coherent movie.

The plot is simple enough: An epidemic rages across the globe killing millions and must be stopped. Mr. Soderbergh, the well-regarded director of “Erin Brockovich,” “Traffic” and several dozen other feature films, has assembled a fine cast. Ms. Paltrow is the aforementioned originator of the pandemic (next time, sweetie, skip the moo shu pork), but Laurence Fishburne, Jude Law, Kate Winslet, Matt Damon, Elliot Gould, Marion Cotillard and Jennifer Ehle are also present. They are all terrific.

And that is one of the problems. There are too many famed performers, too many acting styles, too much to look at. A star cast can get in the way of a story the same way too many big-name musicians can produce a mediocre string quartet or super group rock band. Except for Mr. Damon, who is subsumed in his role as a grieving husband, the actors trump the characters. See Jude Law smirking his way through a television interview. Whoa, check out Ms. Paltrow’s skull being peeled away. And Ms. Cotillard – what a hottie. Either this kind of movie is serious, as this one presumes to be, or it is Hollywood. Or, worse yet, it is “serious Hollywood.” And that is what this one is.

Still, lots of movies survive a big-name cast. More problematic is the cohesion. “Contagion” is never quite sure of its approach. It lurches from God’s-eye overview to serious documentary to pulp sidebar stories, some of which, like Jude Law’s mendacious blogger or Ms. Cotillard’s kidnappers, belong in a trashy B movie.

And while there is a certain tension in the details of trying to figure out How We Will Survive, everyone knows there will be a happy ending, insofar as the world must, Hollywood-style, go on.

There are, nonetheless, some affecting scenes. The movie begins with “Day 2,” and it is not until the last minute that the viewer finds out what happened on “Day 1” to set the virus on its course. This little flashback at the end, almost a coda, is the most affecting and the scariest scene in the movie, because, finally, the viewer sees something true: how easily it can happen.