1. A system for detecting an infectious agent in a sample of cells or a body fluid comprising: an automated composing microscope comprising an array of two or more objective lenses arranged in a row and having the same optical characteristics, each of said two or more objective lenses has its own z-axis movement focusing mechanism; two or more CCD cameras, each connected to one of the said two or more objective lenses and configured to capture the entire field of view of the respective said objective lens; an image acquisition device electrically connected to each of said two or more CCD cameras configured to digitally capture the images acquired by each of said cameras and store said images as an RGB image in an electronic memory; an image processor configured to transform the Red component of the RGB image to a first monochrome grey level image, transform the said first grey level image to a first binary image using a cut off point set to a value indicative of an expected size of the animal cells, operating on said first binary image to remove noise and fill holes, measure size of said first binary image, transform Red component of said RGB image to a second binary image using an expected size of the infectious agent, transform the Green component of said RGB image into a grey level image, form a new grey level image using all pixels having a value equal to a set value M and any grey level value in the Green component in the said RGB image equal to a set value N, transform the said new grey level image into a third binary image, operate on said third binary image to remove noise and fill holes, record the area of the said binary image, and determine whether each said identified animal cell is occupied by said infectious agent.