What is it? Pneumocystosis is a rare disease defined by a fungus infection: Pneumocystis jiroveci. This fungus has infectivity in immunocompromised people whose CD4 count is less than 200 / mm3 of blood. These CD4s are proteins found on the surface of white blood cells, cells of the immune system. Pneumocystis jiroveci infection is said to be opportunistic. Either the fungus […]