Hektoen International

A Journal of Medical Humanities

The American Civil War as a biological phenomenon: Did Salmonella or Sherman win the war for the North?

Michael Brown
Chicago, Illinois, United States


Reexamining Civil War deaths

Civil War

Patients in Ward K of Armory Square Hospital – Washington, DC, 1865


A demographic historian, J. David Hacker, recently discovered an unfortunate truth; using newly digitized data from the 1860, 1870, and 1880 censuses, he constructed new estimates of Northern and Southern Civil War deaths. In his pivotal analysis published in 2012, the death toll in the American Civil War was far higher than previously reported.1 The long-held belief derived from muster-out rolls and battle reports and compiled by amateur historians had previously estimated 618,222 military deaths (360,222 from the North and 258,000 from the South) during the Civil War. Data from the South was particularly untrustworthy, however, due to the post-war destruction of the Southern army and many of its documents. Nonetheless, the previously quoted numbers have stood as accurate totals for the last 150 years. Hacker’s pivotal population study suggests a new number for total war dead at approximately 750,000–800,000 deaths, a 20% increase. Hacker clearly extends our understanding of the carnage and suffering wrought upon the United States by the American Civil War.


Was it bugs or ballistics?

What the new numbers do not reveal is the cause of those deaths. Hacker’s study serves as a reminder that many more of these deaths were related to infectious diseases than to ballistic injuries. It postulates that most of the additional deaths were due to greater medical and disease losses in the South.1 Army records for the North suggest that 62% of Union Army deaths were caused by disease, whereas less accurate Southern records suggest that deaths by disease exceeded 65% of all deaths. By contrast, infectious diseases accounted for 70% of hospital admissions in the Vietnam War, but deaths from infections were less than 0.5% of battle-related causalities.2

A wide variety of biological diseases were noted during the Civil War.3 In order of frequency these were dysentery and diarrheal disorders (Salmonella, Shigella, Amoeba), malaria, measles, typhoid fever and typhus, smallpox, scarlet fever, pneumonia, tuberculosis, “camp itch” (lice infestations), scurvy, rheumatism, mumps, yellow fever, and venereal diseases. Typhoid fever was likely the most common infectious disease of the war, and diarrheal illnesses due to Salmonella and Shigella accounted for significant death and disability.4 Ninety percent of all new recruits to the Confederate Army developed diarrhea upon entering camp, and soldiers on both sides rarely had formed bowel movements. A Southern minister noted, “The disease that seems to breakdown the willpower more than any other was chronic diarrhea, and the patients seemed to lose not only their desire to live but all manliness and self-respect.”5 Medical theory of the early 1860s suffered from a rudimentary concept of hygiene and no knowledge of the infectious causes of illnesses such as dysentery or malaria.6 Without an accurate understanding of the infectious nature of these illnesses, prevention was impossible and spread rapid and complete. It would be ten years before Louis Pasteur’s germ theory would finally begin to alter medical thinking.

The prevailing therapy of medical illness favored the concept of “ill humors” or “noxious effluvia” as causative agents. Indeed, Dr. John Brown’s theory that inflammation represented “excessive stimulation and overexcitement” was widely accepted. Misguided attempts to eliminate these “vapors” and stimulations led to the use of toxic and unnecessary diaphoretics, cathartics, irritants, counter irritants, astringents, emetics, bleedings, and purgatives that further injured or killed the patient.6 These precepts of medical theory, however, did not differ between the North and the South.

The medical corps in the military differed significantly in the North and South, however, which led to significant disparities in medical management.3,7 William Hammond was the U.S. surgeon general for the Union Army until his court-martial in 1864. Hammond, an eleven-year US Army veteran who had spent five years on the faculty of the University of Maryland, was able to run an efficient military medical corps. He ordered hazardous medications out of the formulary, weeded out incompetent physicians, pushed for hygienic conditions, and was able to hire nurses and doctors on the spot as needed. He also invoked the Letterman System, which modernized the use of battlefield ambulances, standardized medical field kits, and restructured the medical command system to favor experience over social status. Hammond’s counterpart in the South, Samuel Preston Moore, was also an army veteran but his attempts to modernize Southern medical care were hampered by social hierarchy, small hospitals, and inadequate physician and nurse staffing. He received a mere $350,000 to initiate medical services for the entire Southern army.5

Demographic factors also played a role in the increased Southern casualties from infectious diseases. Inadequate physical exams, in which unqualified and very young and very old conscripts were brought into the army, increased the morbidity and mortality wrought by infection. A preponderance of troops from rural areas in the South brought individuals into large populations of men where their lack of immunity placed them at a uniquely high risk for infectious disorders. Exposure, lack of clothing and shoes, poor and insufficient foods, and impure water were more pervasive in the Southern ranks, thus increasing their infectious risk.3,4

These differences raise the question: did the Confederate Army’s increased susceptibility to infection, and specifically to diarrheal disorders, lead to a reduction in force that subsequently lost the war? It is important to remember that invasion and conquest were required for the North to win the war, whereas the South needed simply to defend and survive in order to win. It is possible that the South might have succeeded if it had been able to achieve infectious disease rates similar to those in the North.


Contingency points: Vicksburg and Atlanta

Stanford Civil War historian James M. McPherson has noted five critical contingency points during the Civil War where the outcome and duration, far from inevitable at the time, may have significantly changed: 1) McClellan’s failure to capture Richmond, 2) the Union victory at Antietam, 3) The Union victory at Vicksburg, 4) Lee’s loss at Gettysburg, and 5) Sherman’s successful capture of Atlanta.8 The outcomes of two of these five contingency points, the Vicksburg campaign and the capture of Atlanta may have been largely determined by differences in medical care and the toll of infectious diseases. The inability of the South to deal with these diseases and their preferential suffering at the hands of these illnesses placed them in a tenuous situation in both scenarios and may have ensured a victory for the North.

The siege of Vicksburg, Mississippi took place between May 18 and July 4, 1863. The conclusion of the siege, with the surrender of Lieut. Gen. John C. Pemberton’s Confederate defenders, secured the Mississippi River for the North and successfully ended the Vicksburg campaign, strengthening Gen. Ulysses S. Grant’s stature in the Union Army.

Two attempts to control the city by frontal assaults were unsuccessful, forcing Grant to enter a prolonged siege beginning on May 25 and ending with the surrender on July 4. Although Pemberton had only 18,500 troops at his disposal compared to Grant’s 35,000, he had a city with nearly impenetrable defenses. Approximately one-quarter of Grant’s Union Army of the Tennessee was ill with malaria, but overall its medical condition was improving throughout the siege. Conversely, 50% of the Confederate defenders were ill and not with Pemberton’s command at the time of the battle of Champion Hill on May 16, 1863 or later during the siege. It was the loss of this battle that forced Pemberton back into a defensive position around Vicksburg.

Excess Confederate losses from illness were likely due to dysentery syndromes such as Salmonella and Shigella infections, a direct result of water contamination, poor and insufficient food, lack of appropriate clothing with subsequent exposure, and poor hygiene which resulted in infestations of insects and other vermin.4,5These were well-documented issues for those defending Vicksburg and certainly played a role in Grant’s successful siege. One could postulate that if Pemberton’s army had been at full field strength, or even increased by 25% of its size at the Battle of Champion’s Hill, that a repulsed Union Army of the Tennessee would by necessity have fallen back into disarray to the Mississippi River and retreated to Northern-held territory. In this alternate history, Grant, of somewhat tenuous stature in the Union Army, might have lost his command or resigned, leaving Vicksburg and the Mississippi River under Confederate control. This might have prolonged the war beyond 1865, ultimately leaving the South intact as an independent nation through negotiations with the North.

The Battle of Atlanta took place on July 22, 1864 southeast of Atlanta, Georgia. The Union Army under Gen. William Tecumseh Sherman was successful that day in repulsing Gen. Joe Johnston’s Confederate defenders into Atlanta and setting up siege lines around the city. Sherman then proceeded to attempt to cut the city’s supply lines from Macon, Georgia. On August 31, 1864 his army was successful, and on September 2 the city was surrendered to him. Sherman then set up headquarters in the city and remained there until November 15, 1864 when, after burning the majority of the city, he proceeded on his March to the Sea and the capture of Savannah, Georgia.

Sherman’s successful march through the South and capture of Atlanta is typically attributed to his brilliance and ruthlessness as a commander, but perhaps also to Johnson’s hesitation and Confederate Gen. John Bell Hood’s impetuosity.3 It is equally likely, however, that the inability of the Confederate Army to mount an effective defense of Atlanta was due to extraordinary medical losses in its troop strength. Interestingly, any Confederate soldier lost to illness during the Battle of Atlanta never returned to combat. In the last two months of the battle for Atlanta, 30,000 Confederate soldiers were lost to medical transfer and furlough. At the same time, Sherman’s army was considered the healthiest in the Union as it proceeded to live off the land during its march to Atlanta. If the Confederate defenders of Atlanta had a troop health even close to that of the Union Army, an expected increase in true strength of 15,000 to 20,000 soldiers might have stymied Sherman into a stalemate in northern Georgia in 1864. In this alternate history, it is quite possible that Abraham Lincoln might have lost the 1864 election to Gen. George B. McClellan, whose political peace platform called for the cessation of hostilities and negotiations with the Confederacy to allow for its continued existence.


One nation

In our brief review of two of McPherson’s five Civil War contingency points, it seems clear that infectious diseases and specifically dysenteric disorders had a significant impact on the outcome on the war, favoring the North. In the two specific campaigns discussed, those of Vicksburg and Atlanta, diarrheal diseases were decisive in decimating the ranks of Confederate defenders. The South’s significant medical disadvantages and increased risk of infectious diseases ensured a Northern victory. If not for Salmonella typhi, the United States, if it even would even be called that, would be a very different place today.



  1. Hacker JD. A Census-Based Count of Civil War Dead. Civil War History. 2011;57(4):307-348.
  2. Affairs USDoV. Military Health History for Clinicians:Vietnam. Military Health History 2012, 2013.
  3. Freemon FR. Gangrene and Glory: Medical Care during the American Civil War. 1st ed. Urbana, IL: University of Illinois Press; 1998.
  4. Gilchrist MR. Disease and Infection in the American Civil War. The American Biology Teacher. 1998;60(4):258-261.
  5. Cunnignham HH. Doctors in Gray. 2nd ed. Baton Rouge, LA: Louisiana State University Press; 1960.
  6. M.D. CKW. Civil War Medicine. 1st ed. Guilford, CN: The Globe Pequot Press; 1998.
  7. Adams GW. Doctors in Blue. 1st ed. Baton Rouge, LA: Louisiana State University Press; 1952.
  8. McPherson JM. Drawn with the Sword. 1st ed. New York, NY: Oxford University Press; 1996.



MICHAEL D. BROWN, MD, MACM, FACP, FACG, AGAF, is a professor of medicine at Rush University Medical Center in Chicago in the Section of Digestive Diseases. He is particularly interested in the area of functional bowel diseases. As an undergraduate biology major with a history minor at the University of Colorado, he developed a strong academic interest in the American Civil War that continues to this day.


Highlighted in Frontispiece Fall 2013 – Volume 5, Issue 4
Fall 2013  |  Sections  |  War & Veterans

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