The genus Morbillivirus belongs to the virus family Paramyxoviridae, a group of enveloped viruses with non-segmented, negative strand RNA genomes. It contains viruses that are highly infectious, spread via the respiratory route, cause profound immune suppression, and have a propensity to cause large outbreaks associated with high morbidity and mortality in previously unexposed populations. In populations with endemic virus circulation, the epidemiology changes to that of a childhood disease, as hosts that survive the infection normally develop lifelong immunity.
Research on morbillivirus infections has led to exciting developments in recent years. Global measles vaccination coverage has increased, resulting in a significant reduction in measles mortality. In 2011 rinderpest virus was declared globally eradicated – only the second virus to be eradicated by targeted vaccination. Identification of new cellular receptors and implementation of recombinant viruses expressing fluorescent proteins in a range of model systems have provided fundamental new insights into the pathogenesis of morbilliviruses, and their interactions with the host immune system. Nevertheless, both new and well-studied morbilliviruses are associated with significant disease in wildlife and domestic animals. This illustrates the need for robust surveillance and a strategic focus on barriers that restrict cross-species transmission. Recent and ongoing measles outbreaks also demonstrate that maintenance of high vaccination coverage for these highly infectious agents is critical. This article summarizes the most important current research topics in this field.
The identification of cellular receptors and improvement of animal models has provided important new insights into the pathogenesis of morbillivirus infections. It has become clear that all morbilliviruses initially infect cells of the immune system, before they spread to epithelial, endothelial and/or neuronal cells. Morbilliviruses remain a potential cause of disease outbreaks in previously unexposed populations. However, they can also be used to our advantage, as vaccine vectors or as oncolytic viruses. Sustained vaccination coverage and surveillance of circulating morbilliviruses will remain of critical importance for years to come.