The discovery of this new virus will assist in the rapid diagnosis of this disease and help to distinguish it from other diseases caused by pathogens such as A. phagocytophilum, E. chaffeensis, Crimean-Congo hemorrhagic fever virus, Hantavirus, dengue virus, Japanese encephalitis virus, and Chikungunya virus. Furthermore, the availability of the new virus will facilitate the future development of new therapeutic interventions, such as vaccines and drugs. Figure S1 Sensitivity and dynamic range of real-time PCR in the detection of bunyavirus RNA. To evaluate sensitivity of our RT-PCR, a real-time PCR was performed. Serial dilutions of in vitrobtranscribed bunyavirus RNA sequences were tested. A wide linear range (from 5 copies to 5610 7 copies of control RNA per reaction) was detected in this assay. (TIF) Clinical aspects and cytokine response in severe H1N1 influenza A virus infection INTRODUCTION: The immune responses in patients with novel A(H1N1) virus infection (nvA(H1N1)) are incompletely characterized. We investigated the profile of Th1 and Th17 mediators and interferon-inducible protein-10 (IP-10) in groups with severe and mild nvA(H1N1) disease and correlated them with clinical aspects. METHODS: Thirty-two patients hospitalized with confirmed nvA(H1N1) infection were enrolled in the study: 21 patients with nvA(H1N1)-acute respiratory distress syndrome (ARDS) and 11 patients with mild disease. One group of 20 patients with bacterial sepsis-ARDS and another group of 15 healthy volunteers were added to compare their cytokine levels with pandemic influenza groups. In the nvA(H1N1)-ARDS group, the serum cytokine samples were obtained on admission and 3 days later. The clinical aspects were recorded prospectively. RESULTS: In the nvA(H1N1)-ARDS group, obesity and lymphocytopenia were more common and IP-10, interleukin (IL)-12, IL-15, tumor necrosis factor (TNF)α, IL-6, IL-8 and IL-9 were significantly increased versus control. When comparing mild with severe nvA(H1N1) groups, IL-6, IL-8, IL-15 and TNFα were significantly higher in the severe group. In nonsurvivors versus survivors, IL-6 and IL-15 were increased on admission and remained higher 3 days later. A positive correlation of IL-6, IL-8 and IL-15 levels with C-reactive protein and with > 5-day interval between symptom onset and admission, and a negative correlation with the PaO(2):FiO(2 )ratio, were found in nvA(H1N1) groups. In obese patients with influenza disease, a significant increased level of IL-8 was found. When comparing viral ARDS with bacterial ARDS, the level of IL-8, IL-17 and TNFα was significantly higher in bacterial ARDS and IL-12 was increased only in viral ARDS. CONCLUSIONS: In our critically ill patients with novel influenza A(H1N1) virus infection, the hallmarks of the severity of disease were IL-6, IL-15, IL-8 and TNFα. These cytokines, except TNFα, had a positive correlation with the admission delay and C-reactive protein, and a negative correlation with the PaO(2):FiO(2 )ratio. Obese patients with nvA(H1N1) disease have a significant level of IL-8. There are significant differences in the level of cytokines when comparing viral ARDS with bacterial ARDS. Originating from Mexico and spreading initially in the United States and Canada, a novel influenza A(H1N1) virus infection (nvA(H1N1)) of swine origin spread globally during spring 2009 to mid-February 2010. Rates of hospitalization and death have varied widely according to country [1] . Among hospitalized patients 9 to 31% have been admitted to intensive care units (ICUs) where the rate of death was 14 to 46% [2] [3] [4] [5] [6] .