Final answer:
Persons with Rubella are contagious from approximately one week before to one week after the rash appears, with transmission happening via respiratory secretions or sometimes through skin rash or eye secretions.
Step-by-step explanation:
A person with Rubella (German measles) is considered contagious from approximately one week before the onset of the rash to about one week after the rash appears. Transmission can occur through respiratory secretions from coughing or sneezing, or less commonly through contact with the skin rash or eye secretions of the infected individual. This means that the Rubella virus can be spread both by symptomatic as well as asymptomatic carriers. People with Rubella are most contagious when the rash is erupting, but given that nearly half of all infected individuals show no symptoms, contagiousness is not solely dependent on the presence of the rash.
The Rubella virus is a concern particularly in pregnant women because it is teratogenic and can cause congenital rubella syndrome, which may result in severe developmental defects in the fetus. Therefore, it is particularly important to prevent the spread of the Rubella virus to pregnant women, especially during their first trimester.