Rubella is a viral disease which spreads by droplet infection. One attack confers a high degree of immunity. The disease tends to affect older children, adolescents and young adults and it spreads less readily than measles. It occurs mainly in the spring and summer months. The disease in children is trivial. In adults the illness may be more severe, but of short duration and of little importance except when it develops in a woman during the first three to four months of pregnancy. In such cases the child may be born with a congenital malformation such as a cardiac or mental defect, cataract or deafness. The disease is not notifiable. The incubation period is usually about 18 days. A quarantine period is not necessary.