This week the TWiV team explains CRISPR/Cas, the immune system of bacteria and archaea, how novel viruses are discovered by deep sequencing of small RNAs, and the relationship between dry weather and outbreaks of West Nile virus infection.

Vincent, Dickson, and Alan discuss STEP HIV-1 vaccine failure caused by the adenovirus vector, presence of West Nile virus in kidneys for years after initial infection, adaptation of the influenza viral RNA polymerase for replication in human cells, and the significance of the D225G change in the influenza HA protein.

Vincent, Alan, Dick, and Raul Andino recorded TWiV live at the ASM General Meeting in Philadelphia, where they discussed increased arterial blood pressure caused by cytomegalovirus infection, restriction of influenza replication at low temperature by the avian viral glycoproteins, first isolation of West Nile virus in Pennsylvania, and current status of influenza.