Just four pathogens underpin most cases of serious diarrhea in children—the second leading killer of young children worldwide—according to a study published today in The Lancet.

Nature.com reports that out of nearly 40 diarrhea-causing germs, the researchers identified four primary culprits: rotavirus, Cryptosporidium, a toxic type of Escherichia coli, and Shigella. The winnowing of the list could allow health experts to design targeted health campaigns.

“I think what we have done is allow doctors and public health experts to prioritize and potentially save thousands of lives,” says Karen Kotloff, a pediatrician at the University of Maryland, Baltimore, and first author of the study. Diarrheal diseases kill an estimated 800,000 young children each year, second only to pneumonia, which kills around 1.2 million.