of the OHOLO tradition after 8 years of interruption caused by events beyond our control. It is my belief that our uncomp- mising commitment to excellence in research and development in the various areas of science in Israel is essential to our survival in this troubled region. The OHOLO conference tradition is a re?ection of this conviction. The present 46th OHOLO Conference entitled: The Challenge of Highly Pathogenic Microorganisms ¿ Mechanisms of Virulence and Novel Medical Countermeasures intends to address the unique virulence features and ho- pathogen interactions of microorganisms constituting emerging biothreat with emphasis on Y. pestis, B. anthracis, F. tularensis and Orthopox viruses. Accordingly we selected classical microbiological as well as genomic, proteomic & transcr- tomic approaches towards developments of novel prophylactic and post-exposure treatment, as well as updated strategies of diagnostics and bioforensics.