A high fever may manifest in individuals affected by acute chest syndrome. A high fever is any body temperature over 100.9 degrees Fahrenheit or 38.3 degrees Celsius. The high fever that commonly occurs in acute chest syndrome patients can be explained by the fact numerous infections can trigger acute chest syndrome. These infections include respiratory syncytial virus (RSV), pneumonia, sepsis, Streptococcus pneumoniae, Mycoplasma pneumoniae, and Haemophilus influenzae. When the body contracts an infection, the immune system uses its pathogen-fighting mechanisms to try and eradicate the virus or bacteria causing the infection. The immune system uses the body's temperature in an attempt to remove the environment within the body that is allowing the bacteria or virus to grow. Individuals who have sickle cell anemia have a weakened immune system because of its adverse effects on an immunity involved organ called the spleen. A weak immune system causes sickle cell anemia patients to have frequent infections. When one of these infections triggers acute chest syndrome, a high fever is likely to be present.