Viruses are obligate intracellular parasites that rely on the host cell for expansion.
With the development of global analyses techniques like transcriptomics, proteomics and
siRNA library screening of complete cellular gene sets, a large range of host cell factors
have been discovered that either support or restrict virus growth. Here we summarize some
of the recent findings and focus our discussion on the hepatitis C virus and the human
immunodeficiency virus, two major pathogens that threat global health. The identification
of cellular proteins affecting multiple viruses points to the existence of central
regulation nodes that might be exploited for both, a quantitative description of
host-virus interactions within single infected cells and the development of novel,
broad-spectrum antiviral drugs.