This film was a sequel to the very popular "Hawaii" (1966), using unused sections of James Michener's extremely long best-seller for its plot. Charlton Heston had been asked to star in "Hawaii", but had turned it down (he claimed that the producers were uncertain as to whether he should play the missionary or the sea-captain); he may have regretted this, as the film he did appear in during the same year, "Khartoum", was a flop. However, this sequel was panned by critics and had nothing like the earlier film's success.
Although he had declined the original "Hawaii " in 1966. Heston was willing to make this sequel. According to David Shipman's Great Movie Stars- the International Years, Heston was paid $750, 000 plus 10% of the profits.
Original cinematographer Lucien Ballard fell ill during production and was replaced by Philip H. Lathrop.
While much is made of the issue of rats in the Asian slums, it has since come to light that the plague was not carried by infected rats and fleas but that it is airborne. The issue of poor sanitation and crowded living conditions are key to preventing the spread of the plague.