Abraham Lincoln might have been in the early stages of a life-threatening type of smallpox when he delivered his Gettysburg Address, lauded as one of history's greatest speeches and an archetype of genius brevity.

The speech's powerful first words — "Four score and seven years ago ..." — belied a weak and dizzy President Lincoln, concludes a new study.

Nearly one-third of those who contracted this serious form of smallpox in the mid-19th century died — a fate that would have dramatically changed U.S. history had it befallen Lincoln. Though some historians recognize that Lincoln was ill following his Gettysburg speech in 1863, they implicate a mild and non-lethal form of smallpox that occurs in people who have been immunized against the disease.

The finding, published in the current issue of the Journal of Medical Biography, suggests future writings on the 16th president should include the nature and gravity of "Lincoln's Gettysburg Illness."

Being president can be tough. Several presidents have endured odd ailments. And another recent study revealed Lincoln may have suffered from a genetic disorder that destroys nerve cells and could have been responsible for Honest Abe's gangly walk.

Smallpox symptoms

Armond Goldman and Frank Schmalstieg, both of the University of Texas Medical Branch at Galveston, reviewed the symptoms of Lincoln's illness cited in various sources. Then they compared this clinical profile with non-smallpox diseases, including monkeypox, chickenpox and herpes simplex type 1 infections, which could mimic smallpox.

Initially, Lincoln showed signs of being weak and dizzy. During the train trip from Washington, D.C., to Gettysburg, Pa., on Nov. 18, the day before his speech, Lincoln told John Hay, his private secretary and assistant, that he felt weak, according to the researchers.

These symptoms were followed quickly by a high fever, severe headache and backache; within a week, Lincoln's skin erupted with scarlet blisters. The illness lasted three weeks, during which time Lincoln became emaciated, yet his doctors diagnosed the president with a mild form of the disease. Smallpox is caused by either of two closely related pox viruses, called Variola major and Variola minor.

Goldman and Schmalstieg found it was improbable Lincoln suffered from a disease other than smallpox. The pair then looked at the most obvious distinctions between the mild and serious forms of smallpox: duration and severity. Lincoln's symptoms, including the widespread skin lesions and their three-week duration, pointed to the serious type of smallpox.

"Smallpox was rampant in the United States at that time," Goldman said. "In addition, although immunization against smallpox was practiced in the mid-19th century, there is no historical evidence that Lincoln was immunized against smallpox before his illness." Without immunization, Lincoln would surely have been susceptible to the serious form of smallpox.

Another clue supporting their conclusions: "The milder form of smallpox, known as Variola minor, first appeared in the United States at the turn of the 20th century and was unknown in the United States during the mid-19th century when Lincoln became ill," Goldman said.

History changer

The researchers suggest Lincoln's physicians downplayed the severity of his illness in an effort to reassure the public that their president was not dying.

The scientists note such fears would have been well-founded, since the serious form of smallpox was life-threatening. As well, "his death due to smallpox would have undoubtedly changed the subsequent history of the country," Goldman said. "At the least, the goals that were attained during the rest of Lincoln's presidency would have been obtained less rapidly and perhaps less completely."

After a little more than three weeks, Lincoln returned to his full duties and led the country to a successful conclusion to the Civil War in 1865, which ultimately unified the North and South and ended legal slavery in the United States.