The rubella virus is a contagious virus that causes rubella, also known as German measles. It primarily spreads through respiratory droplets when an infected person coughs or sneezes. Symptoms often include a mild rash, fever, and swollen lymph nodes, but many people may not show any symptoms at all. Rubella is particularly concerning for pregnant women, as it can lead to serious birth defects if contracted during the first trimester. Vaccination with the MMR vaccine, which protects against measles, mumps, and rubella, is the most effective way to prevent infection and its complications.