Every time a cell divides, it must replicate its genome exactly once, which it achieves through the parallel action of replication forks. The frequent slowing or stalling of replication forks, termed “replication stress”, is common in both cancer cells and parasites. Replication stress is therefore a common therapeutic target for anti-malarial and cancer chemotherapies, but we have a relatively poor understanding of where, when, why, and how often replication forks stall under these therapies. I will discuss our recent progress towards answering these questions, whereby we are using long-read nanopore DNA sequencing together with AI to measure the movement and stress of thousands of replication forks across the genomes of human cancer cells and malaria parasites.