Risk factors for community-acquired pneumonia with influenza A/H1N1 in southern Israel

Objectives: To determine the risk factors for community-acquired pneumonia (CAP) with influenza A/H1N1 flu in our region. Methods: Adult patients with CAP from July 2009 to February 2010 who were screened for influenza A/H1N1 were identified retrospectively. This was a retrospective case-control study. Cases had CAP with influenza A/H1N1 and controls had CAP without influenza A/H1N1. Patient files were reviewed for demographics, clinical characteristics, treatment, and outcome. Results: Three hundred and eight patients with CAP were identified: 107 cases and 201 controls. For cases vs. controls there were significant differences in the following: median age (40 (range 18-82) vs. 56 (range 18-89) years; p< 0.001), female gender (63.6% vs. 44.3%; p< 0.05), Bedouin Arab origin (41.1% vs. 26.4%; p< 0.05), pyrexia (97.6% vs. 88.5%; p< 0.01), cough (96.3% vs. 75%; p< 0.05), admission to the intensive care unit (18.7% vs. 10.6%; p< 0.05), and CURB-65 score ≥3 (2.8% vs. 11.4%; p< 0.05). Laboratory values including white blood cell (WBC) and platelet counts were lower in cases than in controls, whereas creatine phosphokinase and lactate dehydrogenase levels were higher (p< 0.01). By logistic regression models, young age, Bedouin origin, and lower WBC and platelet counts were independent risk factors for the acquisition of CAP with influenza A/H1N1. Conclusions: In our region CAP with influenza A/H1N1 occurred in younger females of Bedouin Arab origin with less co-morbidity. No difference in mortality was found. We believe that inequalities in socioeconomic conditions could explain our findings.