NIH: Bacterial Pneumonia Caused Most Deaths in 1918 Influenza Pandemic

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Doesn't this make you think we'll soon be seeing a push for the pneumonia vaccine

National Institute of Allergy and Infectious Diseases (NIAID)

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Tuesday, August 19, 2008

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Anne A. Oplinger

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 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.

In a quest to obtain all scientific publications reporting on the pathology and

bacteriology of the 1918-1919 influenza pandemic, Dr. Taubenberger and NIAID

co-author Morens, M.D., 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 that appeared

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," says

Dr. Morens. Pathologists of the time, he adds, 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.

Absent the secondary bacterial infections, many patients might have survived,

experts at the time believed. Indeed, the availability of antibiotics during

the other influenza pandemics of the 20th century, specifically those of 1957

and 1968, was probably a key factor in the lower number of worldwide deaths during

those outbreaks, notes Dr. Morens.

The cause and timing of the next influenza pandemic cannot be predicted with

certainty, the authors acknowledge, nor can the virulence of the pandemic influenza

virus strain. However, it is possible that — as in 1918 — a similar

pattern of viral damage followed by bacterial invasion could unfold, say the

authors. Preparations for diagnosing, treating and preventing bacterial pneumonia

should be among highest priorities in influenza pandemic planning, they write. "We

are encouraged by the fact that pandemic planners are already considering and

implementing some of these actions," says Dr. Fauci. Visit http://www.PandemicFlu.gov for

one-stop access to U.S. Government information on avian and pandemic flu.

NIAID conducts and supports research — at NIH, throughout the United States,

and worldwide — to study the causes of infectious and immune-mediated diseases,

and to develop better means of preventing, diagnosing and treating these illnesses.

News releases, fact sheets and other NIAID-related materials are available on

the NIAID Web site at http://www.niaid.nih.gov.

The National Institutes of Health (NIH) — The Nation's

Medical Research Agency — includes 27 Institutes and

Centers and is a component of the U.S. Department of Health and

Human Services. It is the primary federal agency for conducting

and supporting basic, clinical and translational medical research,

and it investigates the causes, treatments, and cures for both

common and rare diseases. For more information about NIH and

its programs, visit www.nih.gov.Reference: DM

Morens et al. Predominant role of bacterial pneumonia as a cause of

death in pandemic influenza: Implications for pandemic influenza

preparedness. The

Journal of Infectious Diseases DOI: 10.1086/591708 (2008).

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