Division of Viral and Rickettsial Disease, National Center for Infectious Disease, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA

Traditional methods for tracing virus movements within populations have mainly relied upon data obtained by virus isolation and serology. Much more information can be obtained by gene sequence analysis, and the application of the polymerase chain reaction, if necessary combined with reverse transcription, has greatly simplified this procedure. Automated DNA sequence analysis yields data in a form that is available in the computer for comparative analysis with pre-existing databanks. Several examples of the use of sequence analysis will be presented in detail. These will include use of the hemagglutinin or the nucleoprotein gene sequence of measles virus to trace the importation of measles into the USA; analysis of the origin of human rabies cases; tracing the movement of human enteric small round-structured viruses in populations; and the application of gene sequence analysis to detect new influenza virus variants. The information gained from sequence analysis can also be used successfully to develop appropriate strategies for vaccination and control program, and examples will be described.