An animal model that closely mimics a disease in humans gives a huge boost to researchers attempting to combat it. But those developed to date for Middle East respiratory syndrome coronavirus (MERS-CoV), which has caused nearly 900 cases of disease in humans since emerging in Saudi Arabia in 2012 and has killed about one-third of these people, all have serious shortcomings. Although the virus is thought to jump into humans from camels, it’s still unclear whether it causes illnesses in dromedaries. (Besides, camels aren’t exactly known to be cooperative lab animals.) And rhesus macaques, arguably the best model yet developed, rarely develop severe or lethal cases of the disease like humans do. Now, researchers who helped developed the rhesus model think they may have found a much better one: marmosets. They have evidence that MERS-CoV behaves much the same way in these New World monkeys as it does in humans: copying itself to high levels, spreading widely through the lungs, and causing life-threatening pneumonia. What’s more, marmosets and humans have identical amino acids in a critical region of the receptor that MERS-CoV uses to infect cells, they report today in PLOS Pathogens. The development of the marmoset model could have a “major impact” in the search for drugs and vaccines against MERS-CoV, the scientists say.