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 haemagglutination inhibition and neutralising 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 un-immunised 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 time the virus replicates in the nasopharynx and local lymph nodes and then spreads haematogenously 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 immunological basis.