Biosafety Level 4 (BSL4) – Virus Research at the Highest Level of Biosafety and Biosecurity, Volume 121 highlights new advances, with this new volume presenting interesting chapters on highly important topics such as Molecular virulence determinants of human-pathogenic filoviruses, Mucosal Sudan virus infection results in a lethal disease in ferrets with previous Lloviu virus infection not providing cross-protection, Transcriptional signatures of Ebola and Marburg virus infection in a Bat-Immune-System (BIS) mouse model, Divergences in the microbial inactivation pattern between vaporized hydrogen peroxide and aerosolized peracetic acid by dry fogging, and much more.Other chapters cover Molecular expressions in tissues and blood following Reston and Bundibugyo virus infection in swine, De novo rescue of new BSL4 henipaviruses - from sequence to pathogen, Semi-automated diagnostic RT-PCR as a screening assay for antiviral compounds in a 96-well format against highly pathogenic RNA viruses, and Relevance of studying virus – natural reservoir interactions: SNV in deer mice and LASV in Mastomys natalensis. - Provides the latest information on virus research - Offers outstanding and original reviews on a range of virus research topics - Serves as an indispensable reference for researchers and students alike