Measles challenges: global resurgence and factors affecting eradication.

Measles is one of the most highly contagious and inflictive human viral infections, and approximately 90% of exposed individuals become infected following the exposure. The infection is communicable from one day before the prodromal symptom onset until four days after rash onset. Up to 40% of people who attract measles will have other health problems arising during the course of infection. There is no specific treatment for measles. Recent reports highlight that measles infection erases the already existing immune memory of various pathogens. The latest measles outbreaks in sub-Saharan Africa and Europe show the ease with which measles virus can re-enter communities. However, measles outbreaks in recent years have been reported in all regions of the world, including countries that had previously declared the disease eliminated such as United Kingdom and the United States. The present review article provides an outlook of the current epidemiology and challenges to support the global efforts in controlling the disease through discussion on the recent resurgence and enumerating the factors hindering the eradication of measles. This constellation of factors contributing to measles resurgence and outbreak propagation is multifactorial. Key drivers include suboptimal vaccine coverage, stemming from either outright vaccine refusal or barriers to healthcare access leading to incomplete vaccination schedules. This results in a diminution of herd immunity, compromising community-wide protection. Furthermore, primary or secondary vaccine failure, while rare, contributes to a residual pool of susceptible individuals. Diagnostic challenges, including the misdiagnosis of measles as other exanthematous illnesses, can delay outbreak containment and facilitate silent transmission. An epidemiological consequence of prolonged low transmission is an upward shift in the age-specific susceptibility profile, exposing older children and adults who lack natural immunity. Finally, sociopolitical instability, conflict, and resultant internal displacement create conditions conducive to outbreaks by disrupting healthcare infrastructure, hampering vaccination campaigns, and fostering high-density living conditions among vulnerable populations. This review addresses a major gap in measles eradication by integrating scattered evidence on measles resurgence into an integrated comprehensive framework, encompassing health system, epidemiological, immunological, and sociopolitical factors.