2.3. Demographic and Clinical Data

The Spanish CMBD contains routine hospital data, including a diagnosis of legionellosis. All the cases confirmed legionellosis infection, legionellosis testing, or legionellosis-associated respiratory disease. The principal reason for hospitalization was the primary diagnosis code, and admission was considered a single hospital episode. Double-counting admissions that contained several of these diagnoses was avoided. The annual hospitalization rate (HR), average length of hospitalization stay (LOHS), and case-fatality rate (CFR) were calculated using municipal register data. All L-AH in any diagnostic position with the International Classification of Diseases, 9th revision, Clinical Modification ICD-9-CM codes (“482.8” and “482.84”) and ICD-10-CM codes (“A48.1” and “A48.2” from 2016 to 2021) were analyzed. For each case, specific data were gathered on age, sex, average LOHS, HR, and CFR. Groups of age for the study were 0–4, 5–14, 15–24, 25–34, 35–44, 45–54, 55–64, 65–74, 75–84, and >85. First-incidence hospitalizations with a diagnosis of legionellosis were included in the study. In rates by months of age, the number of total newborns and perinatal mortality in Spain were also considered through the Spanish Instituto Nacional de Estadística (INE). For the population denominators by months of age, we assumed a constant birth rate throughout the year to associate the precise hospitalization date for the population at risk in any given month. The CFR was calculated by dividing the number of deaths by the total number of hospitalizations due to legionellosis (%). The average LOHS was calculated [15]. The datasets generated and/or analyzed during the current study are available in the Hospital Discharge Records in the Spanish CMBD repository.

The case notification contains patient demographic information, clinical and diagnostic reports, about the notification process, the severity of the disease, the risk of mortality for the patient, and its impact on the cost of the service. For each record, the following variables were collected: year, autonomous community, Center Type N4, SNS/not SNS, hospital group, cluster group, age, sex, country of birth, country residence, autonomous community residence, province residence, municipality residence, start date contact, date of admission, end date contact, intervention date, contact type, hospital discharge type, origin, contact circumstance, care continuity, ICU admission, ICU days, stay days, principal diagnostic, diagnostics 2–20, POA main diagnosis, POA diagnostics 2–20, procedures 1–20, external procedures 1–6, GRD APR, CDM APR, GRD APR type, APR severity level, APR mortality risk, Spanish weight APR, and APR cost.