Porn for hypochondriacs!
Within the first few minutes of this movie, Gwyneth Paltrow: (a) returns to the US from a business trip to Hong Kong; (b) cheats on her husband; (c) develops a disgusting cough; (d) gets really unattractive for a glamorous movie star; (e) kicks the bucket.
This disconcerts her husband, Matt Damon. (At first, the news goes right over his head.) While moviewatchers might not mind Gwyneth's absence, the movie also kills off Matt Damon's cute stepson with the same disgusting cough. That shows us that things are really serious.
As it turns out, Gwyneth and the kid are just very early casualties of a new virulent disease that spreads worldwide in a matter of days. The movie flits between disease researchers racing to discover the nature of the illness and develop a vaccine, and ordinary people trying to deal with the unravelling social fabric while increasing their odds for survival.
The IMDB points out the massive number of Oscar winners/nominees that appear here: in addition to Matt and Gwyneth, there's Marion Cotillard, Laurence Fishburne, Elliott Gould, John Hawkes, Jude Law, and Kate Winslet. It's not that any of these people actually have to act much, though; mainly they just look scared, confused, devious, or concerned. And, as in Gwyneth's (and, later, Kate's) case, unattractive.
Maybe there should be an Oscar category for that: Most Unattractive Performance by an Ordinarily Good-Looking Actor or Actress.
(There is a very good performance from Jennifer Ehle, playing a dedicated scientist. She hasn't got an Oscar win or nomination yet, but I'm thinking she will someday.)