In a 2005 article published in the Journal, Madeleine Cosman argued that illegal immigrants were carriers of disease, and that immigrants and "anchor babies" were launching a "stealthy assault on [American] medicine."

In the article, Cosman claimed that "Suddenly, in the past 3 years America has more than 7,000 cases of leprosy" because of illegal aliens.

The journal's leprosy claim was cited and repeated by Lou Dobbs as evidence of the dangers of illegal immigration.

Publicly available statistics show that the 7,000 cases of leprosy occurred during the past 30 years, not the past three as Cosman claimed.

James L. Krahenbuhl, director of the U.S. government's leprosy program, stated that there had been no significant increase in leprosy cases, and that "It [leprosy] is not a public health problem—that’s the bottom line."

National Public Radio reported that the Journal article "had footnotes that did not readily support allegations linking a recent rise in leprosy rates to illegal immigrants."

The article's erroneous leprosy claim was pointed out by 60 Minutes, National Public Radio, and The New York Times but has not been corrected by the Journal.