The Biologic Possibility of HIV Transmission During Passionate Kissing

To the Editor.—  Piazza et al¹ report a study that concludes that "passionate" kissing is unsafe. (Actually, they say it is "[not] protective," a curious term. No intimate activity is itself "protective" against human immunodeficiency virus [HIV] transmission, although using a condom, for example, may be. I assume the authors mean "not protected" or "unsafe.") I find this conclusion doubtful.Since the authors base their conclusion on the presence of blood in saliva, I assume they agree that the saliva itself is not of major concern in HIV transmission.² It is only the blood—and only that quantity of blood transferred between partners—that results in infection. Further, it is infected leukocytes that are of concern, not free virus.³I present some rough calculations, always erring on the side of overestimating the infection risk: Assume that all of the after-kissing increase in saliva hemoglobin concentration found by Piazza et