The 1918 to 1919 H1N1 influenza pandemic is among the most deadly events in recorded human history, having killed an estimated 50 to 100 million persons. Recent H5N1 avian influenza epizootics associated with sporadic human fatalities have heightened concern that a new influenza pandemic, one at least as lethal as that of 1918, could be developing. In early 2009, a novel pandemic H1N1 influenza...

Much information is available for the 2009 H1N1 influenza immunity response, but little is known about the antibody change in seasonal influenza before and during the novel influenza A pandemic. In this study, we conducted a cross-sectional serological survey of 4 types of major seasonal influenza in March and September 2009 on a full range of age groups, to investigate seasonal influenza immun...

BACKGROUND Several studies have shown a relatively high mortality rate among young people infected by the 2009 pandemic influenza A (H1N1) virus. Here we compared the age distributions of morbidity and mortality during two seasonal influenza epidemics (H1N1 and H3N2) in France and the United States with those of the 2009 H1N1 pandemic waves in the same countries. METHODS Age-standardized rati...

BACKGROUND Seasonal influenza activity varies with geography and time of year. OBJECTIVE To describe how pandemic influenza A(H1N1)2009 [A(H1N1)pdm09] activity varied during the 2009-2010 pandemic. METHODS We analyzed influenza virological data compiled by the World Health Organization from June 2009-August 2010. We calculated weekly proportions of A(H1N1)pdm09-positive specimens out of all...

BACKGROUND During the 2009 pandemic of influenza A virus subtype H1N1 (A[H1N1]pdm09) infection, older individuals were partially protected from severe disease. It is not known whether preexisting antibodies with effector functions such as antibody-dependent cellular cytotoxicity (ADCC) contributed to the immunity observed. METHODS We tested serum specimens obtained from 182 individuals aged 1...

In previous influenza pandemics, studies of autopsy specimens have shown that most deaths attributed to influenza A virus infection occurred concurrently with bacterial pneumonia, but such evidence has been lacking for 2009 pandemic influenza A (H1N1). To help determine the role of bacterial coinfection in the current influenza pandemic, CDC examined postmortem lung specimens from patients with...

BACKGROUND In contrast to seasonal influenza epidemics, where the majority of deaths occur amongst elderly, a considerable part of the 2009 pandemic influenza related deaths concerned relatively young people. In the Netherlands, all deaths associated with laboratory-confirmed influenza A(H1N1) 2009 virus infection had to be notified, both during the 2009-2010 pandemic season and the 2010-2011 i...

During the spring of 2009, a new influenza A (H1N1) virus of swine origin emerged and spread worldwide causing a pandemic influenza. Here, 329 naso-pharyngeal swabs collected from patients with flu-like symptoms were analyzed by real-time PCR for the presence of H1N1 2009 pandemic virus. Twenty-five samples collected from immunocompetent and immunodepressed patients contained the H1N1 pandemic ...

Elevation of liver transaminase levels is a frequent observation during systemic infections. The aim of our study was to investigate liver damage during pandemic 2009 influenza A/H1N1 infection in comparison with seasonal influenza. Serum levels of aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transpeptidase (GGT) were significantly higher in patients with pandemic in...