As previously indicated molecular epidemiology has been critical to demonstrating the interruption of indigenous measles transmission in the United States and the continuing role importation plays in determining the annual burden of disease. Similarly, cases of rubella are rare, and in the case of poliomyelitis due to wild poliovirus infection, absent, within the United States. However, both diseases are still endemic in other countries, and thus, importation into the United States is expected. A failure to detect these expected cases of disease indicates our surveillance is not sensitive enough and, thus, requires improvements be made to detect these cases.