Togaviridae and Flaviridae These are two families of virus that contain small, enveloped, a single stranded and a +ve RNA genome Except Rubella all Togavirus are arboviruses Except for Hepatitis C all Flaviviruses are arbovirus.

Rubella Virus Laboratory diagnosis: serological test for presence of anti rubella IgM antibodies or a four fold increase of IgG antibodies which conform diagnosis of rubella.

Pathogenesis a) Initial noncytolytic infection is established in the upper respiratory tract and then spread to the local lymph nodes. b) viremia spread virions to the skin and other tissue C) Shedding of virions into respiratory droplets occur during two weeks prodromal period and as for long as weeks following onset of the rash. d) Transplacental infection in non immune pregnant women leads to viral replication in fetal tissue and possible teratogenic effect due to alterations in fetal growth, mitosis, and chromosome structure. e) Antiviral antibody appears after viremia and helps limit virion spread.

Diseases due to Rubella Virus A) German Measles: Rubella In children the disease is benign, consisting of swollen glands, and a pink maculopapular rash that last 3 days, starting on the face and spreading downward over trunk and extremities. In adult, the disease is more severe, with arthralgia, arthritis, thrombocytopenia (rare) and a possible postinfectionous due to immune response.

b). Congenital rubella: Transplacental infection of fetus until 20th week of gestation can lead to cataracts , mental retardation and deafness. Maternal anti-rubella antibodies resulting from earlier infection or vaccination prevent viral spread to the placenta and fetus.

Transmission and Prevention. Rubella virus is spread by the respiratory route only Prevention: Routine Immunization is done with live attenuated virus as part of MMR.