Measles erases immune memory for years after the rash fades
Measles is among the most contagious human infections: about nine in ten non-immune household contacts catch it. After the rash, “immune amnesia” can wipe antibody memory to other pathogens for up to two to three years—raising later childhood deaths—while the vaccine’s weakened strain does not deplete that memory.
Symptoms usually appear ten to twelve days after exposure and last seven to ten days: high fever often over 40 °C (104 °F), cough, runny nose, inflamed eyes, then Koplik spots inside the mouth, then a face-first red flat rash. People shed virus from four days before to four days after rash onset. Airborne droplets stay infectious up to two hours. Common complications include diarrhea (eight percent), middle-ear infection (seven percent), and pneumonia (six percent); about thirty percent of cases see some immediate complication. Encephalitis, blindness, and rare fatal subacute sclerosing panencephalitis also occur.
The measles virus is a single-stranded RNA morbillivirus with twenty-four strains in eight clades, closest to eradicated rinderpest and canine distemper. It invades airway immune cells via hemagglutinin binding SLAM (CD150), then rides macrophages and lymphocytes through lymph nodes and spleen like a Trojan horse. No specific antiviral cure exists; care is supportive—rehydration, nutrition, fever control, antibiotics for secondary bacterial infections, and vitamin A for children under five. U.S. deaths were 0.2 percent of reported cases from 1985–1992 but can reach ten percent with malnutrition; African case fatality may hit six percent settled and thirty percent in refugee settings.
Vaccination cut measles deaths about eighty percent between 2000 and 2017; by 2017 roughly eighty-five percent of children worldwide had a first dose. Herd immunity needs more than ninety-five percent coverage because transmission is so efficient. Global deaths fell from 2.6 million in 1980 to 73,000 by 2014, yet cases and deaths rose again after 2017 as vaccination slipped. The disease still hits about ten million people yearly, mainly in parts of Africa and Asia, and remains a leading vaccine-preventable killer—humans are its only confirmed natural host.
Source: Measles
