Fluorescent micrograph showing a section of human appendix infected with the measles virus. The measles virus is shown in green, cytokeratin is shown in red, which marks the epithelium, and Dapi staining highlights the cell nucleus in blue. Measles is highly contagious virus transmitted though contact with mucous membranes of an infected person (mouth or nose) or airborne water droplets. It is primarily a respiratory disease and symptoms include coughing, sneezing, high fever and can lead to pneumonia.