Characteristics of Rubella
Member of the togavirus family
ssRNA positive-sense enveloped virus
Spread by respiratory droplets and transplacental.
In the prevaccination era, 80% of women were already infected by childbearing age.
Risks of rubella infection during pregnancy
Preconception minimal risk
0-12 weeks 100% risk of fetus being congenitally infected resulting in major congenital abnormalities.Spontaneous abortion occurs in 20% of cases.
13-16 weeks deafness and retinopathy 15%
after 16 weeks normal development, slight risk of deafness and retinopathy
Member of the herpesvirus
Lipoprotein envelope, derived from the nuclear membrane
Genome: linear, ds DNA
Replicate in the nucleus
Humans are the natural hosts
Giant cell formation (Cytomegalo)
Primary infection usually asymptomatic. Virus then becomes latent and is reactivated from time to time.
Transmitted by infected saliva, breast milk, sexually, transplacental and through infected blood and organ transplantation.
60% of the population eventually become infected. In some developing countries, the figure is up to 95%.
Neonatal Herpes Simplex
The baby is usually infected perinatally during passage through the birth canal.
Premature rupturing of the membranes is a well recognized risk factor.
The risk of perinatal transmission is greatest when there is a florid primary infection in the mother.
There is an appreciably smaller risk from recurrent lesions in the mother, probably because of the lower viral load and the presence of specific antibody.
The baby may also be infected from other sources such as oral lesions from the mother or a herpetic whitlow in a nurse.