The measles virus is a highly contagious virus that causes measles, a serious illness characterized by fever, cough, runny nose, and a distinctive red rash. It spreads through respiratory droplets when an infected person coughs or sneezes. The virus can remain in the air for up to two hours after an infected person leaves the area, making it easy to transmit. Measles can lead to severe complications, including pneumonia, encephalitis, and even death, especially in young children and those with weakened immune systems. Vaccination with the measles, mumps, and rubella (MMR) vaccine is the most effective way to prevent infection and protect public health.