In February, a young woman visited an urgent care clinic complaining of painful vaginal ulcers. The differential diagnosis of genital ulcers is interesting. Common sexually transmitted infections such as gonorrhea and chlamydia don’t cause ulcers, but syphilis, herpes, chanchroid do (as do other diseases, but they are not common in the U.S.). Syphilis is typically painless, so most painful genital ulcers turn out to be herpes, and sometimes chanchroid. She revealed to the doctors that she had recently had sex with her boyfriend, a soldier who had just been vaccinated against smallpox. The clinic treated her for chanchoid and herpes, as well as gonorrhea and chlamydia, and perhaps cellulitis. She didn’t get better.
The history of smallpox vaccination is pretty cool. In fact, the word “vaccination” comes from the name of the virus used to immunize against smallpox. The vaccinia (“cowpox”) virus was used in the first inoculations against smallpox, and is still the basis for current vaccines. It is also used in a very clever way to help vaccinate animals against rabies. Smallpox is not the safest vaccine, and given that the disease has been eradicated, the risk-benefit ratio rarely justifies its use, which is currently restricted to certain military personnel, lab workers, and first responders.
To vaccinate people against smallpox, vaccinia, a closely related virus, is injected into the skin causing a localized infection. This infection produces an antibody response and memory response. Because vaccinia and smallpox are so closely related, the antibody response is close enough to give immunity to both cowpox and smallpox. But that viral infection on the upper arm can be problematic, as this weeks Morbidity and Mortality Weekly Report illustrates.
After being treated for multiple STDs, the young woman went to another doctor because her rash was worse. He attempted to test her for cowpox, but sent off the wrong sort of tube and the specimen couldn’t be tested. The infectious disease expert he referred her to collected the correct specimen, and she eventually healed.
The Epidemiology Intelligence Service (EIS) investigated and found that her boyfriend had removed the bandage from his vaccination site, and that their sexual activity had included digital vaginal manipulation.
This is really cool for a variety of reasons. STDs are common, and the presenting lesions were not atypical of some common STDs. Still, the doctors were handed the data that she had been potentially exposed to vaccinia. But vaccinia is vanishingly rare, and patients are often ignored. The next doctor tried to do the right thing, but made the same mistake many of us would likely make—he sent a swab for a viral disease in a standard viral medium, which turned out to be wrong.
It’s often said that most diagnoses can be made with a careful history and physical exam. It’s also said that when you hear hoofbeats, you should think of horses rather than zebras. In this case, a careful history and physical might have revealed to an astute clinician that a zebra was in the room.
This isn’t the first report of cowpox being sexually transmitted, but it’s the first one I’ve ever read about. I guess I’ll be adding this to my differential for genital ulcers.
Centers for Disease Control and Prevention (CDC) (2010). Vaccinia virus infection after sexual contact with a military smallpox vaccinee — washington, 2010. MMWR. Morbidity and mortality weekly report, 59 (25), 773-5 PMID: 20592687