Chen Yi-ming points out that male genitalia are less likely to develop sores, and the mucus membranes in female sexual organs have a larger number of monocytes that are receptive to viruses. In addition, seminal fluid contains more viruses than vaginal fluid. For these reasons, women are more easily infected by men than vice versa.
陳宜民指出，由於男性性器官比較不容易有傷口、女性黏膜上接受病毒的單核細胞數量較多、精液的病毒量較陰道內的病毒多，因此女性較容易被男性感染。