Unless you are a disease-vector biologist studying in the field in West Africa, don’t attempt this explanation at home.
Brian Foy, a researcher from Colorado State University, spent several months in 2008 trapping mosquitoes in the remote town of Bandafassi, Senegal, as part of a study on malaria. He worked with his graduate student, Kevin Kobylinski, and both men got bitten a lot. (More on Time.com: Lovers Can’t Agree on Whether They Agreed to Monogamy)
About five days after the men came home in August 2008, they got sick. Both developed fatigue, rash, headaches, and painfully swollen joints. Foy also had pain when urinating and blood in his semen. A few days after that, it became clear that Foy’s wife, Joy Chilson Foy, a nurse at the Poudre Valley Hospital in Fort Collins, had caught whatever her husband had picked up. She had symptoms of malaise, chills, headache and sensitivity to light. Mysteriously, the couple’s four children remained healthy. Within about a week, most symptoms started receding in all three patients.
Exactly what happened when Foy and Kobylinski returned from Senegal on 24 August 2008 has remained a mystery for years. … The scientists suspected they were infected through one of their many mosquito bites but were stumped as to the pathogen. So were several laboratories, including the U.S. Centers for Disease Control and Prevention (CDC), whose lab for insect-borne diseases is in Fort Collins. Antibody tests on serum samples from the two scientists tested positive for dengue, a viral disease that might have explained the symptoms, but samples from Chilson Foy came back negative. “Eventually, the CDC said, ‘We think you had dengue, but we don’t know what your wife had,'” says Foy, who decided to keep samples from all three in the freezer.
A year later, over a couple of beers back in Senegal, Kobylinski described the mystery sickness to a colleague, who immediately hypothesized that it could be the Zika virus, an obscure illness that occurs in southeastern Senegal and is transmitted primarily through mosquitoes. Not much is known about it; it is rarely reported and often misdiagnosed as the more common dengue fever. (More on Time.com: NDM-1 Superbug Mutation Found in New Delhi Drinking Water)
After returning home in December 2009, Kobylinski told Foy about Zika, and the scientists had all their samples re-tested. They had a winner: antibodies to the Zika virus showed up in all three samples (the reason the researchers’ samples initially appeared to show antibodies to dengue is because they had been vaccinated for the yellow fever virus, which is closely related to dengue).
There were only 14 Zika cases reported in the medical literature until 2007, when an outbreak on the Micronesian island of Yap affected 73% of the population, largely those between 30 and 59, and sickened 50% more women than men — a ratio that hinted at the virus’ sexual transmissibility. With most sexually transmitted infections, vaginal intercourse poses a higher risk of infection for women than for men. (More on Time.com: Study: Women With Circumcised Partners May Have Lower HPV Risk)
Foy wrote his case study [PDF] himself — which was published in this month’s issue of Emerging Infectious Diseases — referring to himself as “Patient 1,” Kobylinski as “Patient 2,” and his wife as “Patient 3.” Reported ScienceNOW:
There is no direct evidence that Foy’s wife was infected through sexual contact, but the circumstantial evidence is strong. It’s very unlikely that she was infected by a bite by a mosquito that first bit her husband; the three tropical Aedes mosquito species known to transmit Zika don’t live in northern Colorado, and moreover, the virus has to complete a two-week life cycle within the insect before it can infect the next human; Foy’s wife fell ill just nine days after his return. And yes, as the paper puts it, “patients 1 and 3 reported having vaginal sexual intercourse in the days after patient 1 returned home but before the onset of his clinical illness.” (“My wife wasn’t happy with what happened afterwards,” Foy adds.)
If so, Foy’s case could be the first documented sexual transmission of an insect-borne disease. Hopefully his wife thinks it was worth it for the sake of science.