Ninety-one percent of those autopsied had underlying medical conditions, such as heart disease or respiratory disease, including asthma, before becoming ill with 2009 H1N1 influenza. Seventy-two percent of the adults and adolescents who died were obese. This finding agrees with earlier reports, based on hospital records, linking obesity with an increased risk of death from 2009 H1N1 influenza.
The researchers examined tissue samples from the 34 deceased individuals to assess how 2009 H1N1 influenza virus damaged various parts of the respiratory system. "We saw a spectrum of damage to tissue in both the upper and lower respiratory tracts," says Dr. Taubenberger. In all cases, the uppermost regions of the respiratory tractthe trachea and bronchial tubeswere inflamed, with severe damage in some cases. In 18 cases, evidence of damage lower down in the finer branches of the bronchial tubes, or bronchioles, was noted. In 25 cases, the researchers found damage to the small globular air sacs, or alveoli, of the lungs.
"This pattern of pathology in the airway tissues is similar to that reported in autopsy findings of victims of both the 1918 and 1957 influenza pandemics," notes Dr. Taubenberger.
The researchers also examined 33 of the 34 cases for evidence of pulmonary bacterial infections. Of these cases, 18 (55 percent) were positive for such infections. Not all of those individuals who had bacterial pneumonia along with 2009 H1N1 virus infection had been hospitalized, however, indicating that some had acquired their bacterial infections outside of a health-care setting. This raises the possibility, say the authors, that community-acquired bacterial pneumonia is playing a role in the current pandemic. "Even in an era of widespread and early antibiotic use," write the authors, "bacterial pneumonia remains an important factor for severe or fatal influenza."
|Contact: Anne A. Oplinger|
NIH/National Institute of Allergy and Infectious Diseases