Coloured transmission electron micrograph (TEM) of West Nile virus particles (gold) replicating within the cytoplasm of an infected VERO E6 cell (pink). West Nile virus (WNV) particles (Flavivirus sp.). The virus is an arbovirus (arthropod-borne virus) and is transmitted to humans and other mammals from infected birds through the bite of a mosquito vector. Symptoms can range from a mild fever to spontaneous bleeding of the skin and circulatory failure, which are often fatal. Image captured at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland, USA.