Why does the flu kill?
Brazilian researchers have analyzed the results of the first autopsies of patients who died as a result of Infection with the H1N1 flu virus.
The researchers examined 21 patients who died in São Paulo in July and August 2009 and in whom the diagnosis of H1N1 flu was confirmed by biological analyzes. The results of their study will be published in the January 1 issue of the Journal of the American Thoracic Society of Respiratory Medicine and Critical Care.
Most of the patients examined by the doctors were between 30 and 59 years old. Three-quarters (76 percent) of them had underlying conditions such as heart disease or lung cancer, but as noted by practitioners since the beginning of the epidemic, for a quarter of the patients no other pathology exists. has been found. All presented a progressive and rapidly fatal form of the disease.
While previous data have shown that most patients with nonfatal infection have fever, cough and body aches (myalgia), Dr. Mauad, an associate professor in the Department of Pathology at the University of São Paulo Paulo, Brazil, noted that "the majority of patients with a lethal form of the disease had difficulty breathing (dyspnea), fever, but little or no muscle pain. "
All patients died from aggravated pulmonary lesions but there were three distinct patterns of lesions: "All patients have an image of acute lung injury, in some patients this is the predominant pattern, for some lung involvement is associated with necrotizing bronchiolitis while in others there is a bleeding tendency, "says Dr. Mauad.
"Patients with necrotizing bronchiolitis are more likely to have bacterial co-infection. Patients with heart disease and cancer are more likely to have a bleeding disorder. It is important to keep in mind that patients with underlying medical conditions should be properly monitored as they are at higher risk of developing severe H1N1 infection, "he adds.
The researchers also found evidence of a "cytokine storm," an aberrant immune response in the lungs of some individuals, which is almost certainly implicated in the pathogenesis of these fatal cases. It is possible that the virus entering the lungs triggers a disproportionate inflammatory response that damages lung tissue.
Further research is needed to understand precisely how and why some patients succumb to fatal progression when infected with H1N1. These early works establish a foundation by defining the histological structures associated with a deadly infection.