Bacterial pneumonia caused most deaths in 1918 flu pandemic

August 20th, 2008 - 3:00 pm ICT by IANS  

Washington, Aug 20 (IANS) Bacterial pneumonia, not flu virus alone, accounted for the bulk of deaths during the 1918 pandemic, according to researchers from the National Institute of Allergy and Infectious Diseases (NIAID).Bacteria normally inhabiting the nose and throat caused the pneumonia by invading the lungs, along a pathway created by the flu virus that destroyed cells lining bronchial tubes and lungs.

A future flu pandemic may unfold in a similar manner, concluded the authors of the study. Therefore, comprehensive pandemic preparations should include not only efforts to produce new or improved flu vaccines and antiviral drugs but also provisions to stockpile antibiotics and bacterial vaccines as well.

“The weight of evidence we examined from both historical and modern analyses of 1918 influenza pandemic favours a scenario in which viral damage followed by bacterial pneumonia led to the vast majority of deaths,” said co-author and NIAID director Anthony S. Fauci. “In essence, the virus landed the first blow while bacteria delivered the knockout punch.”

NIAID co-author and pathologist Jeffery Taubenberger examined lung tissue samples from 58 soldiers who died of flu at various US military bases in 1918 and 1919. The samples, preserved in paraffin blocks, were re-cut and stained to allow microscopic evaluation.

In most cases, he added, 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.

In a quest to obtain all scientific publications reporting on the pathology and bacteriology of the 1918-1919 pandemic, Taubenberger and NIAID co-author David Morens, searched bibliography sources for papers in any language.

They also reviewed scientific and medical journals published in English, French and German, and located all papers reporting on autopsies conducted on influenza victims.

From a pool of more than 2,000 publications between 1919 and 1929, the researchers identified 118 key autopsy series reports. In total, the autopsy series they reviewed represented 8,398 individual autopsies conducted in 15 countries.

The published reports “clearly and consistently implicated secondary bacterial pneumonia caused by common upper respiratory flora in most influenza fatalities,” said Morens.

Pathologists of the time, he added, were nearly unanimous in the conviction that deaths were not caused directly by the then-unidentified influenza virus, but rather resulted from severe secondary pneumonia caused by various bacteria.

Indeed, the availability of antibiotics during later flu pandemics, specifically those of 1957 and 1968, was probably a key factor in the lower number of worldwide deaths during those outbreaks, noted Morens.

These findings will appear in the Oct 1 issue of The Journal of Infectious Diseases and are now available online.

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