Matonaviridae

Matonaviridae contains a single genus, Rubivirus, with Rubella virus as its sole recognized human pathogen. Rubella virus is an enveloped, positive-sense ssRNA virus transmitted via respiratory droplets. It causes a mild febrile illness in children and adults characterized by a fine maculopapular rash starting on the face and spreading caudally, postauricular/suboccipital lymphadenopathy, and low-grade fever; arthralgias are common in adult women. The major clinical concern is congenital rubella syndrome (CRS), which occurs when a non-immune pregnant woman is infected, especially during the first trimester, leading to a classic triad: sensorineural deafness, cataracts (and other eye defects), and congenital heart defects (patent ductus arteriosus, pulmonary artery stenosis). Other findings can include microcephaly, intellectual disability, 'blueberry muffin' rash (extramedullary hematopoiesis), and hepatosplenomegaly. Diagnosis involves serology (IgM for acute infection, IgG for immunity) and PCR. Prevention is via the live attenuated MMR vaccine, which is contraindicated in pregnancy. Historically, rubella virus was grouped with alphaviruses in Togaviridae due to similar morphology and genome organization, but phylogenetic and structural differences (e.g., unique fusion protein, lack of an arthropod vector) led the ICTV to create the new family Matonaviridae in 2018.