Returning to Washington by train the afternoon after giving the Gettysburg Address, Lincoln developed a severe headache and fever (31–34). When he arrived back in Washington, the President was placed at bed rest, while complaining of increasing headache, backache, fever and generalized fatigue. Two days later the rash appeared. The diagnosis of smallpox was made, and for the next three weeks Lincoln remained under quarantine at the White House. The case was mild, but upon recovery, Lincoln’s face became pockmarked. His illness lasted slightly less than one month although, like George Washington, he did not recover his full strength until nearly two months later. The White House was placed on “penetrable quarantine,”

"How and where Lincoln became infected are not clear (28,31,34). The most common belief is that Lincoln was infected by his young son, Todd, who had an illness and rash diagnosed, likely mistakenly, as “scarlatina” when Lincoln left Washington for Gettysburg. No evidence has ever surfaced that Lincoln was vaccinated. Although Lincoln survived his smallpox infection, during its course death remained a strong possibility. So, when the news of his illness eventually did leak out, the prospect caused major concern, not only in North America, but also in Europe. China and Japan both lost emperors to smallpox, and centuries earlier rulers of European countries had died of smallpox. In Washington, Congress sent prayers for the president’s recovery, and those visiting the president were vaccinated. Even so, Lincoln’s valet, William Johnson, suffered a severe smallpox infection. United States Senator Lemuel Bowden, Republican for Virginia, became infected and died of smallpox."