Chronic lymphocytic leukemia or the CLL is among the most common type of leukemia affecting the adults. The lymphocytic leukemia starts in the lymphocytes. Lymphocytic leukemia is different from the lymphoma (which also occur in the lymphocytes) as it only occurs in the bone marrow and the blood. The person suffering from CLL is susceptible to an array of infections. Among the various infectious agents, the CLL patient is the most susceptible to the Staphylococcus aureus. This agent causes skin infections, pneumonia, toxic shock syndrome and many other life threatening diseases. The person becomes susceptible to its attack as the immunity of his is weakened beacuse of the damage to the lymphoctic cells.
In the population with a large number of individuals, the mutation would only have a small impact, while a population with only 18 individuals would result in a very large i off as the mutation would be in a greater percentage of the population.