Sera of persons of different age groups collected in 1976, 1978 and 1979 were tested for the presence of HI antibodies against various strains of the H3N2 and H1N1 subtypes of influenza virus. The occurrence of infection by H3N2 subtype was recorded during the 1976-1978 period but in 1979, circulation of this subtype of virus was limited. The prevalence of antibody against A/São Paulo/1/78 (H1N...

In their recent paper, Peter Palese and Taia T. Wang proposed a hypothesis to explain how an older circulating subtype of influenza A virus is replaced with a novel subtype (1). They and others also published experimental evidence supporting their hypothesis on the extinction of seasonal H1N1 viruses by the 2009 pandemic H1N1 viruses (2). Although they discussed only the disappearance of season...

background: guillain-barre syndrome (gbs) is an acute immune-mediated peripheral neuropathy usually after an incident. this study was performed to investigate the basic epidemiologic features of gbs in south of iran. methods: we studied consecutive patients with gbs in nemazi hospital of shiraz, southern iran. demographic characteristics of the subjects, i.e. age, sex, and length of hospital st...

background: both influenza a virus (iav) and respiratory syncytial virus (rsv) cause acute respiratory infection (ari) in infants and young children. this study was conducted to determine influenza a virus and its co infection with rsv among the hospitalized children with ari. methods: a total of 153 throat samples of the hospitalized young children aged between below one year and 5 years with ...

Pandemic influenza A (H1N1) 2009 (pandemic H1N1) is spreading throughout the planet. It has become the dominant strain in the Southern Hemisphere, where the influenza season has now ended. Here, on the basis of reported case clusters in the United States, we estimated the household secondary attack rate for pandemic H1N1 to be 27.3% [95% confidence interval (CI) from 12.2% to 50.5%]. From a sch...

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...

Among the influenza A viruses (IAVs) in wild aquatic birds, only H1, H2, and H3 subtypes have caused epidemics in humans. H1N1 viruses of avian origin have also caused 3 of 5 pandemics. To understand the reappearance of H1N1 in the context of pandemic emergence, we investigated whether avian H1N1 IAVs have contributed to the evolution of human, swine, and 2009 pandemic H1N1 IAVs. On the basis o...

The purpose of this study was to understand the geographic extent, risk factors, and attack rate of the 2009 pandemic influenza A (H1N1) virus [A(H1N1)pdm09] infection in Shandong Province, China and to identify the influencing factors. A randomized serological survey of A(H1N1)pdm09 infection was carried out in August and September 2010. A total of 4,549 participants involved in the survey ...

Antibody-dependent enhancement of the uptake of influenza A virus by Fc receptor-bearing cells was analyzed by using virus strains of the three human influenza A virus subtypes, A/PR/8/34 (H1N1), A/Japan/305/57 (H2N2), and A/Port Chalmers/1/73 (H3N2). Immune sera obtained from mice following primary infection with an H1N1, H2N2, or H3N2 subtype virus neutralized only virus of the same subtype; ...

The H1N1 subtype of influenza A virus has caused substantial morbidity and mortality in humans, first documented in the global pandemic of 1918 and continuing to the present day. Despite this disease burden, the evolutionary history of the A/H1N1 virus is not well understood, particularly whether there is a virological basis for several notable epidemics of unusual severity in the 1940s and 195...