The First Influenza Pandemic of the 21st Century

Abstract

The 2009 H1N1 influenza virus (formerly known as swine flu) first appeared in Mexico and the United States in March and April 2009 and has swept the globe with unprecedented speed as a result of airline travel. On June 11, 2009, the World Health Organization raised its pandemic level to the highest level, Phase 6, indicating widespread community transmission on at least two continents. The 2009 H1N1 virus contains a unique combination of gene segments from human, swine and avian influenza A viruses. Children and young adults appear to be the most affected, perhaps reflecting protection in the elderly owing to exposure to H1N1 strains before 1957. Most clinical disease is relatively mild but complications leading to hospitalization, with the need for intensive care, can occur, especially in very young children, during pregnancy, in morbid obesity, and in those with underlying medical conditions such as chronic lung and cardiac diseases, diabetes, and immunosuppression. Bacterial co-infection has played a significant role in fatal cases. The case of fatality has been estimated at around 0.4%. Mathematical modeling suggests that the effect of novel influenza virus can be reduced by immunization, but the question remains: can we produce enough H1N1 vaccine to beat the pandemic?

Infection by H1N1 flu virus revealing T-cell acute lymphoid leukaemia: about two cases

“…No secondary infections were observed, and neither patient experienced ARDS, perhaps due to the neutropaenia, despite the fact that previously reported deaths were mostly due to ARDS [2,3]. The only recommended treatment for the H1N1 virus is oseltamivir, and this treatment is highly effective [4][5][6][7]. We confirmed the efficacy in immuno-compromised patients.…”

Swine influenza A (H1N1) virus infection in infants

“…Fig. 1 Note diffuse radio-opacities on both lung fields on chest radiography of case 5 obtained at second day of hospitalization Children less than 1 year old are also known from previous pandemics to be at increased risk of complications [1]. As with our cases, the outcomes of these infants may have been influenced by antiviral oseltamivir therapy.…”

Modifications in the Polymerase Genes of a Swine-Like Triple-Reassortant Influenza Virus To Generate Live Attenuated Vaccines against 2009 Pandemic H1N1 Viruses

“…The virus spread easily and sustainably among humans throughout the world, prompting the World Health Organization (WHO) to declare on 11 June 2009 the first influenza pandemic of the 21st century (1,18). This new isolate was identified as a swine-origin influenza virus (S-OIV), because its RNA segments were most closely related to influenza viruses isolated from pigs in North America and Eurasia (19,20).…”