Novel findings from the second wave of adult pH1N1 in the United States.

Objective: To describe the impact of novel pH1N1 virus in Atlanta, GA, for inpatient and intensive care services, including lung lavage data and determinants of disease outcome, from the earliest group of infected US population after initial cases.

Design: An observational review of all patients with laboratory-confirmed pH1N1 disease hospitalized in four Atlanta hospitals from August 1 through October 31, 2009. Data reviewed included demographics, anthropometrics, clinical laboratory, and respiratory physiology.

Setting: Four hospitals in urban Atlanta, Georgia.

Patients: Consecutively admitted patients between August 1 and October 31, 2009 with laboratory confirmed pH1N1 infection.

Interventions: None.

Measurements And Main Results: A total of 109 patients were admitted during the surveillance period and intensive care unit care was required in 23 patients (21%) among which there were six deaths (26%). Only eight of the 109 (7%) patients were without medical comorbidity; 34% of the 65 female patients were pregnant and none died or required intensive care unit care. Patients with respiratory failure undergoing bronchoalveolar lavage exhibited neutrophilic predominance (average 64%) and negative bacterial cultures. Body mass index was > 30 kg/m in 35 of 81 (43%) of patients with anthropometric data and 16 of 23 (70%) patients requiring intensive care unit care (p = .03). The 16 patients who required mechanical ventilation (70% of intensive care unit patients) were characterized by severe hypoxemia (requiring high levels of inspired oxygen and positive end-expiratory pressures), reduced lung compliance, and high lung injury scores.

Conclusions: This first report of the second wave of US pH1N1 disease from Atlanta, GA, shares epidemiologic characteristics of earlier cohorts but differs by having an even greater prevalence of obesity and fewer patients who were free from chronic medical conditions. Importantly, lung lavage fluid in severe pH1N1 disease is predominantly neutrophilic and culture-negative. Further reports are needed to validate these new findings regarding pH1N1 disease in the United States.