BACKGROUND A recrudescent wave of pandemic influenza A/H1N1 is underway in Mexico in winter 2013-14, following a mild 2012-13 A/H3N2 influenza season. Mexico previously experienced several waves of pandemic A/H1N1 activity in spring, summer and fall 2009 and winter 2011-2012, with a gradual shift of influenza-related hospitalizations and deaths towards older ages. Here we describe changes in th...

BACKGROUND Cross-immunity between seasonal and pandemic A/H1N1 influenza viruses remains uncertain. In particular, the extent that previous infection or vaccination by seasonal A/H1N1 viruses can elicit protective immunity against pandemic A/H1N1 is unclear. METHODOLOGY/PRINCIPAL FINDINGS Neutralizing titers against seasonal A/H1N1 (A/Brisbane/59/2007) and against pandemic A/H1N1 (A/Californi...

INTRODUCTION While there is much information about the burden of influenza A(H1N1)pdm09 in North America, little data exist on its burden in South America. METHODS During April to December 2009, we actively searched for persons with severe acute respiratory infection and influenza-like illness (ILI) in three sentinel cities. A proportion of case-patients provided swabs for influenza testing. ...

BACKGROUND Hypercytokinemia is the main immunopathological mechanism contributing to a more severe clinical course in influenza A (H1N1) virus infections. Most patients infected with the influenza A (H1N1) pdm09 virus had increased systemic levels of pro-inflammatory cytokines; including interleukin IL-6, IL-8, and tumor necrosis factor-alpha (TNF-α). We propose that single-nucleotide polymorph...

INTRODUCTION Haemagglutination-inhibition (HI) antibody titer is a correlate of protection against influenza; its persistence after infection or vaccination is important to determining susceptibility to subsequent infection. Few studies, however, have reported longitudinal data regarding the magnitude and duration of HI protection following natural seasonal influenza A infection. METHODS Usin...

We describe the clinical characteristics and outcomes of adults hospitalized with pneumonia during the pandemic (H1N1) 2009 outbreak. Patients admitted to a general hospital in San Luis Potosí, Mexico, from April 10 through May 11, 2009, suspected to have influenza virus-associated pneumonia were evaluated. We identified 50 patients with suspected influenza pneumonia; the presence of influenza ...

In this report, we describe the occurrence of two novel swine influenza viruses (SIVs) in pigs in Argentina. These viruses are the result of two independent reassortment events between the H1N1 pandemic influenza virus (H1N1pdm) and human-like SIVs, showing the constant evolution of influenza viruses at the human-swine interface and the potential health risk of H1N1pdm as it appears to be maint...

During the influenza season 2007-8, the proportion of seasonal influenza A(H1N1) viruses resistant to the neuraminidase inhibitor oseltamivir increased worldwide. We conducted an investigation to compare patients infected with oseltamivir-resistant (ose-R) and oseltamivir- susceptible (ose-S) influenza A(H1N1) viruses regarding risk factors for resistance and the capability to transmit in the h...

BACKGROUND The recent influenza A/H1N1 pandemic has caused considerable morbidity and some mortality and is therefore a severe threat to certain individuals. Up to 31 January 2010, there had been 1,229 confirmed deaths from Influenza A/H1N1 in India. METHODOLOGY This study was a retrospective analysis of deaths caused by RT-PCR-confirmed cases of Influenza A/H1N1 in a tertiary care institutio...

BACKGROUND Acute respiratory infections are a leading cause of morbidity and mortality worldwide. Starting in 2009, pandemic influenza A(H1N1) 2009 virus has become one of the leading respiratory pathogens worldwide. However, the overall impact of this virus as a cause of mortality has not been clearly defined. OBJECTIVES To determine the impact of pandemic influenza A(H1N1) 2009 on mortality...