Grim autopsies: H1N1, a true killer in some cases
Shades of 1918
Though a growing sense of public apathy threatens to reduce H1N1 influenza A to the Rodney Dangerfield of pandemics, those who have experienced or witnessed a severe case of infection will not soon forget this erstwhile "swine flu." A thin spectrum of highly severe cases has occurred since the virus first appeared, and a newly published study indicates that trend continues for an unlucky minority of people.
In fatal cases of 2009 H1N1 influenza, the virus can damage cells throughout the respiratory airway, much like the viruses that caused the 1918 and 1957 influenza pandemics, report researchers from the National Institutes of Health (NIH) and the New York City Office of Chief Medical Examiner. The scientists reviewed autopsy reports, hospital records, and other clinical data from 34 people who died of 2009 H1N1 influenza infection between May 15 and July 9, 2009. All but two of the deaths occurred in New York City. A microscopic examination of tissues throughout the airways revealed that the virus caused damage primarily to the upper airway — the trachea and bronchial tubes — but tissue damage in the lower airway, including deep in the lungs, was present as well. Evidence of secondary bacterial infection was seen in more than half of the victims.
The team was led by Jeffery K. Taubenberger, MD, PhD, of the National Institute of Allergy and Infectious Diseases (NIAID) at NIH. The findings are reported in the Archives of Pathology & Laboratory Medicine, now available online and scheduled to appear in the February 2010 print issue.1
The new report also underscores the impact 2009 H1N1 influenza is having on younger people. While most deaths from seasonal influenza occur in adults over 65 years old, deaths from 2009 H1N1 influenza occur predominately among younger people. The majority of deaths (62%) in the 34 cases studied were among those 25 to 49 years old; two infants also were among the fatal cases. 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," Taubenberger says. "In all cases, the uppermost regions of the respiratory tract—the trachea and bronchial tubes — were inflamed, with severe damage in some cases.
Reference
- Gill JR, Sheng Z, Ely SF, et al. Pulmonary pathologic findings of fatal 2009 pandemic influenza A/H1N1 viral infections. Arch Pathol Lab Med 2010;134:E1-E9. Published in advance of print at: http://arpa.allenpress.com/arpaonline/?request=index-html.
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