A relic of its era, and as a result it has a certain charm: a Europudding all star disaster film about a virus loose on a train travelling through Europe, with a cast that features something for everyone: Richard Harris (then at the height of his weird 70s career as an action star, that also included Golden Rendezvous and The Wild Geese) as a doctor; Sophia Loren in a role that is actually superfluous to the plot even though the producer was her husband (this happened surprisingly often in Loren films producer by her husband); Lee Strasberg in just his second film role as a Jew who doesn't want to go to Poland and who makes the inevitable comments about gas, camps and showers (were there no other offers after Godfather Part 2?); Lionel Stander as a porter in a part that led to his casting in Hart to Hart; OJ Simpson as a priest but actually an FBI agent; Harris' then wife Ann Turkel as a singer with long hair and a tendency to be seen in bikini briefs despite the fact the movie is mostly set on a, well, train; Ava Gardner as a woman of mystery accompanied by a drug addicted toy boy Michael Sheen (wide eyed and long haired and quite good); Burt Lancaster as a general quite willing to have the train go off a bridge so that America's involvement in germ warfare won't be exposed. (There's a strong strain of anti-Americanism through the movie which may have helped up the American bagging of the film... a similar thing happened with the much superior Quantum of Solace.)
It's a bit of a mess of a movie with a bunch of subplots and no one seems really at home but everyone appears to try. I think it was a mistake to stop the train and have everyone inspected- it slowed down momentum. And the ending isn't that satisfying - I wanted Lancaster to get more of a come uppance or to more clearly get away with it.
The film does get points for sending half the train over the bridge and killing heaps of passengers. And that cast is always likeable.