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Researchers Find New Patterns in H1N1 Deaths NEW YORK -- December 23, 2009 -- Researchers have performed an autopsy study to examine the precise causes of death in victims of the influenza A(H1N1) virus. The results will be published in the January 1 issue of the American Journal of Respiratory and Critical Care Medicine. “The lack of information on the pathophysiology of this novel disease is a limitation that prevents better clinical management and hinders the development of a therapeutic strategy,” said lead author, Thais Mauad, MD, Department of Pathology, São Paulo University, São Paulo, Brazil. The researchers examined 21 patients who had died in São Paulo with confirmed H1N1 in July 2009 and August, 2009. Most were aged between 30 and 59 years. They found that 76% of the patients had underlying medical conditions such as heart disease or cancer, but there was no clear complicating medical condition in the remaining quarter. All presented a progressive and rapidly fatal form of the disease. While previous data has shown that most patients with a non-fatal infection have fever, cough and myalgia, Dr. Mauad noted that “most patients with a fatal form of the disease presented with dyspnea, with fever and myalgia being less frequently present.” All patients died of severe acute lung injury, but there were 3 distinct patterns of the damage to their lungs, indicating that the infection killed in distinct ways. “All patients have a picture of acute lung injury,” said Dr. Mauad. “In some patients this is the predominant pattern; in others, acute lung injury is associated with necrotising bronchiolitis; and in others there is a haemorrhagic pattern.” “Patients with necrotising bronchiolitis are more likely to have a bacterial co-infection,” he continued. “Patients with heart disease and cancer are more likely to have a haemorrhagic condition in their lungs. It is important to bear in mind that patients with underlying medical conditions must be adequately monitored, since they are at greater risk of developing a severe H1N1 infection.” “We found that 38% of these patients had a bacterial infection,” said Dr. Mauad. “This has important consequences because these patients need to receive antibiotic therapy, in addition to antiviral therapy.” The researchers also found evidence of an influenza-associated ‘cytokine storm,’ an aberrant immune response in the lungs of certain individuals, which was almost certainly involved in the pathogenesis in these fatal cases of the H1N1 infection. “[This] suggests that an overly vigorous host inflammatory response triggered by the viral infection may spill over to and damage lung tissue, thereby causing acute lung injury and fatal respiratory failure,” noted John Heffner, MD, Providence Portland Medical Center, Portland, Oregon. Further research is needed to understand precisely how and why certain patients succumb to a fatal progression when infected with H1N1. While most patients experience a mild illness with no lasting effects, this research lays important groundwork for future efforts by defining the histological patterns associated with a fatal infection. “We would like to deepen our efforts into the understanding of the immune responses in cases of severe infection,” said Dr. Mauad. “This could ultimately lead to new therapeutic approaches.” SOURCE: American Thoracic Society E-mail this page to a friend or colleague! To print, use this version