Researchers have created a compact and portable device that can test human blood samples for the presence of antibodies against measles and rubella in only 35 minutes. The new technology allows for on-the-spot assessment of a person's vulnerability to these vaccine-preventable diseases (VPDs) - which remain a major health concern in developing countries. Each year, measles causes an estimated 134,000 deaths, and rubella results in an estimated 100,000 children born with birth defects such as deafness. What's more, displaced populations such as refugees are especially susceptible to VPDs due to malnutrition, lack of healthcare, and low vaccination coverage. Serosurveys - assays that analyze blood samples for the presence of antibodies against a VPD - allow health authorities to determine the risk of outbreaks in a population and evaluate the progress of immunization programs. However, existing tests require access to infrastructure such as centralized laboratories, cold storage and transportation, making them difficult to conduct in remote settings where they are needed most. To overcome this hurdle, Alphonsus Ng and colleagues created the Measles-Rubella Box (MR Box), a technology that can rapidly test multiple blood samples for antibodies against measles and rubella. It utilizes inexpensive, inkjet-printed digital microfluidic cartridges that manipulate blood samples into discrete fluid droplets. The authors tested their device in the field by gathering blood samples from 144 children and caregivers in a refugee camp in Kenya, and compared their results to reference tests. Although the MR Box does not yet match the accuracy of lab-based serosurveys, Ng et al. say it represents a potentially useful tool for a range of global health applications that require portable and low-cost analysis.