This application requests funds to enable U.S. scientists, particularly young investigators, postdoctoral fellows, and predoctoral students to attend the Fifth International Positive-Strand RNA Virus Symposium in St. Petersburg, FL, May 23 to 28, 1998. The symposium organizer is Margo A. Brinton, Georgia State University. The scientific program will be organized with the aid of a Program Committee. Eight plenary sessions and one short talk session will contain talks on 3D-structure analysis of viruses and viral proteins; Viral entry mechanisms (receptors, penetration and uncoating); RNA expression, replication, transcription and recombination; RNA virus vectors; Viral Immunology; Viral Pathogenesis (tropism, virulence and spread of virus replication and antivirals). Eight families of animal viruses, eighteen families of plant viruses, one family insect viruses and one family of bacteriophages are positive-strand RNA viruses. Diseases caused by positive-strand RNA viruses are of medical, agricultural, and economic significance. Human encephalitis, poliomyelitis, heart disease, hepatitis, the common cold, gastroenteritis, hemorrhagic fever, and birth defects can be caused by positive-strand RNA viruses. Positive-strand RNA virus infections are often fatal in patients immunosuppressed due to cancer, transplantation, or AIDS. Previous International Positive-Strand RNA Virus Symposia were held in 1986, 1989, 1992 and 1995. Because of the broad-based international attendence of the symposium, the conference site alternates between the U.S.A. and Europe. All four of the previous meetings were extremely successful in achieving the goal of promoting discourse and scientific collaboration between animal, plant, and insect virus researchers.