The measles virus, also called rubeola virus, is an enveloped, single‑stranded, negative‑sense RNA virus in the genus Morbillivirus within the family Paramyxoviridae. It infects only humans and causes measles, a highly contagious febrile illness characterized by cough, coryza, conjunctivitis and a maculopapular rash.
Virology & Pathogenesis
The measles virus genome encodes six structural proteins (nucleoprotein, phosphoprotein, matrix, fusion, haemagglutinin and large polymerase) and two non‑structural proteins. It is an enveloped, negative‑sense RNA virus belonging to the genus Morbillivirus in the family Paramyxoviridae【145865728069587†L164-L172】. Viral entry begins when the haemagglutinin protein binds to cellular receptors such as the immune cell receptor CD150 (SLAM) and epithelial receptor nectin‑4, facilitating fusion via the F protein. Replication occurs in the cytoplasm, and progeny virions bud from the plasma membrane. Infection starts in the respiratory tract, spreads to regional lymphoid tissues and then disseminates via viremia. Measles is among the most contagious human viruses; transmission occurs by respiratory droplets and small aerosols, and the virus remains viable in the air or on surfaces for hours【145865728069587†L105-L111】. Each case can infect 14‑18 susceptible individuals when introduced into a non‑immune population. There are no animal reservoirs, so sustained transmission depends on a continuous chain of susceptible humans. After the initial prodrome, the virus induces transient immunosuppression by interfering with interferon signaling, predisposing patients to secondary infections.
Clinical features and impact
After an incubation of 10–14 days, measles presents with the classic prodrome of fever, cough, coryza and conjunctivitis, followed by Koplik spots on the buccal mucosa and a cephalocaudal maculopapular rash. Most cases resolve within a week of rash onset, but complications are common. Primary viral pneumonia and secondary bacterial pneumonia are major causes of mortality; other complications include otitis media, diarrhea, acute encephalitis and the rare degenerative neurologic disease subacute sclerosing panencephalitis. Measles during pregnancy increases the risk of miscarriage and preterm birth. Malnutrition and vitamin A deficiency worsen outcomes, and supplemental vitamin A reduces morbidity. Global vaccination programs using the live attenuated measles‑mumps‑rubella (MMR) vaccine drastically reduced incidence, and measles was declared eliminated in several regions. However, outbreaks continue when vaccination coverage declines; the CDC reported 935 U.S. cases in the first four months of 2025【145865728069587†L105-L115】, underscoring the need for maintaining herd immunity.
Measles virus remains a leading cause of vaccine‑preventable childhood mortality worldwide. High vaccination coverage, prompt identification of cases and supportive care are crucial to control this highly contagious virus.
Related Terms: Morbillivirus, Rubeola, MMR vaccine, Koplik spots, Paramyxovirus