Bacterial Pneumonia Caused Most Deaths in 1918 Influenza Pandemic
Implications for Future Pandemic Planning
The majority of deaths during the influenza pandemic of 1918-1919 were not caused by the influenza virus acting alone, report researchers from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. Instead, most victims succumbed to bacterial pneumonia following influenza virus infection. The pneumonia was caused when bacteria that normally inhabit the nose and throat invaded the lungs along a pathway created when the virus destroyed the cells that line the bronchial tubes and lungs.
A future influenza pandemic may unfold in a similar manner, say the NIAID authors, whose paper in the Oct. 1 issue of The Journal of Infectious Diseases is now available online. Therefore, the authors conclude, comprehensive pandemic preparations should include not only efforts to produce new or improved influenza vaccines and antiviral drugs but also provisions to stockpile antibiotics and bacterial vaccines as well.
The work presents complementary lines of evidence from the fields of pathology and history of medicine to support this conclusion. “The weight of evidence we examined from both historical and modern analyses of the 1918 influenza pandemic favors a scenario in which viral damage followed by bacterial pneumonia led to the vast majority of deaths,” says co-author NIAID Director Anthony S. Fauci, M.D. “In essence, the virus landed the first blow while bacteria delivered the knockout punch.”
NIAID co-author and pathologist Jeffery Taubenberger, M.D., Ph.D., examined lung tissue samples from 58 soldiers who died of influenza at various U. S. military bases in 1918 and 1919. The samples, preserved in paraffin blocks, were re-cut and stained to allow microscopic evaluation. Examination revealed a spectrum of tissue damage “ranging from changes characteristic of the primary viral pneumonia and evidence of tissue repair to evidence of severe, acute, secondary bacterial pneumonia,” says Dr. Taubenberger. In most cases, he adds, the predominant disease at the time of death appeared to have been bacterial pneumonia. There also was evidence that the virus destroyed the cells lining the bronchial tubes, including cells with protective hair-like projections, or cilia. This loss made other kinds of cells throughout the entire respiratory tract — including cells deep in the lungs — vulnerable to attack by bacteria that migrated down the newly created pathway from the nose and throat.