Researchers now have clear new targets and insights for developing a Shigella vaccine. Having more than 150 non-human primates at a research center fall ill with diarrhea in a stomach-churning outbreak that flowed for over two years doesn’t sound much like good fortune. But for some scientists, it kind of was, providing a heaping pile of valuable data on how they might finally defeat a foul foe.

In a study published in the latest issue of Science Translational Medicine, scientists sifted through the dump of immunological data from the infections, logging new ways to train immune cells to defeat the bacteria behind the outbreak, a type of Shigella. Researchers were able to pluck out specific bits of the bacteria that the immune system could most effectively attack, linking specific target molecules to specific types of germ-busting immune responses.

The outbreak began in December 2022 at the Wisconsin National Primate Research Center in Madison. In all, there were 169 microbiologically confirmed shigellosis cases among the non-human primates. Researchers collected 151 Shigella isolates for serotyping and did whole genome sequencing on 95 representative isolates. Of the 90 isolates tested for antimicrobial resistance, more than half (63 percent) were multidrug resistant.

The researchers drew serum, plasma, and specific types of immune cells from 41 infected animals across their infections. The study “revealed unexpected features of the anti-Shigella antibody response in naturally infected [non-human primates] and represents a step toward the rational design of Shigella vaccine candidates,” the authors write. Shigella strikes more than 200 million people each year and kills more than 200,000, mostly children.