From Wikipedia:
https://en.wikipedia.org/wiki/The_Cassandra_Crossing
The Cassandra Crossing is a 1976 disaster thriller film directed by George Pan Cosmatos and starring Sophia Loren, Richard Harris, Ava Gardner, Martin Sheen, Burt Lancaster, Lee Strasberg and O. J. Simpson about an infected Swedish terrorist who infects a train's passengers as they head to a derelict arch bridge.
With the backing of the media tycoon Sir Lew Grade (the head of the British broadcast network Associated Television) and the Italian film producer Carlo Ponti, the international all-star cast was expected to attract a widespread audience, with rights sold prior to filming, to both British and American distributors. Ponti also saw the production as a showcase for his wife, Sophia Loren.
Enjoy,
Janor