[Epidemiology of infections in neutropenic patients]

Epidemiological data are useful to determine changes in forms of clinical expression and in the microbial agents causing infections. This allows empirical or preemptive treatments to be designed and can guide diagnostic tests. Empirical data also allow patients to be classified by risk group in order to decide on the need for hospitalization. The incidence of neutropenia is increasing as a result of the more aggressive antineoplastic treatments used and the broader age range of patients who receive them. It has been calculated that in the USA neutropenia causes approximately 60,000 hospitalizations per year and that a third of these occur in hematological patients. The most frequent foci of infection are: pneumonia (38%), bacteremia (35%) and urinary (11%). Of the bacteria causing infection, two thirds are Gram-positive and the remaining bacilli are Gram-negative. In the last few years, an increase of Gram-negative bacteria seems to have reemerged. The incidence of fungal isolates represents 2-10%, depending on the type of neutropenic patient analyzed. Fungal isolates are found preferentially in patients with prolonged neutropenia and/or other associated immunodeficiencies, as occurs in allogenic bone marrow transplantation or in patients who have received purine analogs. Viruses are very frequent. Respiratory viruses seem to be emerging pathogens in this group of patients.