On a rainy afternoon on Valentine’s Day, students and faculty filled the seminar room of the East Asian Studies Center to hear Professor William Johnston lecture on sexually transmitted disease in feudal Japan.

The lecture, entitled “Love’s Disease in East Asia: How Syphilis Went Native in Japan,” incorporated threads of biology, economics, linguistics, historiography, and anthropology into a narrative account of how Johnston stumbled upon a historical mystery and solved it through extensive research (and meditation).

He began the lecture on the concept of “love,” and how East Asian, specifically Chinese and Japanese, equivalents of the English word carry very different connotations than that of the West. The Chinese word “ai” is bound up with Buddhist and Confucian principles of compassion and social responsibility. Thus, the idea of love and sexual practices was not always conflated as it is in Western conceptions of romantic love. Johnston pointed out that anxieties over venereal disease and pregnancy—the physical consequences of intercourse—are as much bound up with sexual practices as love is.

The mystery that Johnston sought to unravel was the disjuncture between the rise in economic growth in seventeenth to nineteenth century Japan and the relative stability Japan’s population at the time. For Johnston, this was a historical anomaly.

Johnston describes the “Aha!” moment that occurred to him in the middle of a Buddhist meditation retreat he was attending at the time—“Does syphilis cause infertility?” Syphilis was introduced to Japan in the sixteenth century from China, and was first called the “foreign disease,” then the “plum disease” because of the red rashes that appeared on the body during the first stages of infection.

Johnston compared Japan’s initial naming of the disease as “foreign” with the tendency in European history to attribute the origin of syphilis to a neighboring country, or “the other.”

“To the French, it was the ’Italian disease;’ To the English, it was the ’French disease;’ and to the Russians, it was the ’German disease,’” he explained.

Syphilis entered China via the Portuguese, who frequently traded in southern Chinese port cities such as Canton, Hong Kong from where it eventually spread into Korea and ultimately to Japan.

After some online research, Johnston found Syphilis could not have been responsible for female reproductive infertility.

“That was a ’hmmm’ moment” Johnston joked.

He expanded his research into other diseases prevalent in Edo-period Japan, and we hit on Chlamydia as a possible suspect. The scientific name for the disease is Chlamydia trachomatis—trachoma. It turned out that one of the physical effects of Chlamydia is blindness, which was rampant in Japan during that time. Johnston knew that Chlamydia causes a chain reaction of infections—pelvic inflammatory disorder causes inflammation of the fallopian tubes, which could in turn lead to female infertility. The mystery was solved.

“I learned this from my research on tuberculosis that the role of disease cannot be underestimated,” Johnston concluded.

Disease ecology, he stated, underlines the power of the environment and health to fundamentally shape human civilizations and human history.

I-Hsiao Chen ’08 said that she was surprised by some of the social practices Johnston discussed in his lecture, referencing in particular the fact that female virginity was not at all prized in Edo-period Japan.

In fact, Johnston explained, a man could refuse to marry a woman if she was still a virgin, as having intercourse with an inexperienced partner on the first night of marriage was considered unpleasant for the groom.

“It was really interesting,” said Maya Bery ’08, a student in Johnston’s “History of Disease and Epidemics.” “It’s not immediately obvious the causes of a population [discrepancy] like that, but in retrospect it makes sense.”