Humanitarian emergencies and infectious diseases have a mutually negative impact on one another. Crisis settings like refugee camps, war zones and communities hit by natural disasters are often plagued by factors that increase the risk and severity of infectious diseases. Malnutrition, poverty, crowding, complicating health issues and minimal or no access to medicine and other treatment services are common, and increase the importance of disease prevention efforts like immunization and clean water. At the same time, the unchecked spread of potentially vaccine-preventable diseases in these communities can further destabilize already fragile communities and dramatically increase suffering.