Robert Ludlum's "The Cassandra Compact"

Lt. Colonel Jon Smith, currently working as a medical researcher, is contacted by a Russian colleague with an urgent request that they meet in Venice in ten days. When they meet, however, his colleague is killed almost instantly in a hail of automatic gunfire but not before he passes on to Smith the vital intelligence - someone is out to steal Russia's store of the smallpox virus. Completely irradicated, smallpox is the deadliest of viruses and could well cause an epidemic of unheard of proportions should it be unleashed on the population at large. Smith, with the help of his colleagues at Covert-One, must prevent the virus from being stolen. But his adversaries are several steps ahead of him and now he must find and stop the conspirators before they loose Armageddon upon the world.