Rubella

Rubella is caused by rubella virus, which is a togavirus and the only member of the genus Rubivirus. Humans are the only natural host. The virus has a positive-stranded RNA genome and a glycolipid envelope. There is only 1 antigenic type. Rubella virus is readily inactivated by chemical agents, low pH, heat, and cold. It can be cultivated in a variety of cell lines. Cell-mediated immunity develops 2 to 4 weeks after infection and hemagglutination inhibition and neutralizing antibodies directed against the virus peak at approximately 4 weeks. Immunity following rubella usually persists for life, although recurrent infection has been reported. Rubella vaccines are reported to be approximately 97% effective in preventing disease after a single dose.[12]McLean HQ, Fiebelkorn AP, Temte JL, et al; Centers for Disease Control and Prevention. Prevention of measles, rubella, congenital rubella syndrome, and mumps, 2013: summary recommendations of the Advisory Committee on Immunization Practices. MMWR Recomm Rep. 2013 Jun 14;62(RR-04):1-34. https://www.cdc.gov/mmwr/preview/mmwrhtml/rr6204a1.htm http://www.ncbi.nlm.nih.gov/pubmed/23760231?tool=bestpractice.com Most rubella infections in the US are imported from countries in which rubella is endemic and affects unimmunized people.

Rubella is transmitted from human to human only by direct or droplet contact with infected body fluids, most commonly nasopharyngeal secretions.[7]Lanzieri T, Haber P, Icenogle JP, et al. Rubella. In: Hamborsky J, Kroger A, Wolfe C, eds. CDC The Pink Book: Epidemiology and prevention of vaccine-preventable diseases. Aug 2021 [internet publication]. https://www.cdc.gov/vaccines/pubs/pinkbook/rubella.html Patients may shed infectious virus from 7 to 30 days after infection (from 1 week before to 2 weeks after the onset of rash). However, infants with congenital rubella syndrome may be contagious for >1 year. The average incubation period is 17 days (range: 12 to 23 days), during which the virus replicates in the nasopharynx and local lymph nodes and then spreads hematogenously throughout the body (including, in pregnant women, to the placenta and fetus).[5]Centers for Disease Control and Prevention. Rubella (German measles, three-day measles). Dec 2020 [internet publication]. https://www.cdc.gov/rubella/index.html ​ Systemic symptoms are due to viral infection, but some manifestations (rash, thrombocytopenia, arthritis) probably have an immunologic basis.