Novel influenza A (H1N1) infection vs. common influenza-like illness: a prospective study.

BACKGROUND: On June 11th, 2009 the World Health Organization (WHO) declared the first influenza pandemic of the 21st century. Data regarding the clinical characteristics and course of this viral infectious disease are still being assessed. The aim of this study was to investigate and compare the possible differences in clinical course and outcome between H1N1-positive [H1N1(+)] and negative [H1N1(-)] patients. MATERIAL/METHODS: This prospective study was conducted between July 2009 and January 2010 in a regional hospital in Greece. The study population consisted of 165 patients aged 14 years or older, with influenza-like illness (ILI) who, according to CDC recommendations, fulfilled the criteria for diagnostic influenza testing. Enrolled patients underwent a detailed diagnostic work-up. Infection by the H1N1 virus was diagnosed using real-time reverse transcriptase polymerase chain reaction, from pharyngeal swab specimens. RESULTS: We identified 81 H1N1 (+) (49%) patients. Statistical analysis revealed that H1N1(+) patients were significantly younger (median age 27 vs. 35 years, p<0.05), had a decreased white blood cell count (median 7.200 vs. 8.415, p<0.05) and an increased percentage of monocytes (55.6% vs. 27.4%, p<0.05) compared to the H1N1(-) patients. The clinical presentation at the emergency department, as well as the hospital admission and disease complication rate, were not significantly different between the 2 groups. CONCLUSIONS: The clinical characteristics of the new influenza virus appear to be mild and to resemble those of common influenza-like illnesses (ILI). The patients who tested positive for the H1N1 virus were younger and had an increased percentage of monocytes compared to the H1N1-negative patients.

Early alterations of the innate and adaptive immune statuses in sepsis according to the type of underlying infection.

INTRODUCTION: Although major changes of the immune system have been described in sepsis, it has never been studied whether these may differ in relation to the type of underlying infection or not. This was studied for the first time. METHODS: The statuses of the innate and adaptive immune systems were prospectively compared in 505 patients. Whole blood was sampled within less than 24 hours of advent of sepsis; white blood cells were stained with monoclonal antibodies and analyzed though a flow cytometer. RESULTS: Expression of HLA-DR was significantly decreased among patients with severe sepsis/shock due to acute pyelonephritis and intraabdominal infections compared with sepsis. The rate of apoptosis of natural killer (NK) cells differed significantly among patients with severe sepsis/shock due to ventilator-associated pneumonia (VAP) and hospital-acquired pneumonia (HAP) compared with sepsis. The rate of apoptosis of NKT cells differed significantly among patients with severe sepsis/shock due to acute pyelonephritis, primary bacteremia and VAP/HAP compared with sepsis. Regarding adaptive immunity, absolute counts of CD4-lymphocytes were significantly decreased among patients with severe sepsis/shock due to community-acquired pneumonia (CAP) and intraabdominal infections compared with sepsis. Absolute counts of B-lymphocytes were significantly decreased among patients with severe sepsis/shock due to CAP compared with sepsis. CONCLUSIONS: Major differences of the early statuses of the innate and adaptive immune systems exist between sepsis and severe sepsis/shock in relation to the underlying type of infection. These results may have a major impact on therapeutics.