When Brian Foy returned home to America from a field trip in Senegal, Africa, he didn’t know he was infected with the mosquito spread Zika virus.
But just a few days later he was sick with extreme fatigue and joint pain, and so was his wife Chilson. A new study coauthored by the pair and colleagues suggests that this is the first documented case of an insect-borne disease being transmitted sexually.
Though the paper lists the patients as Anonymous, in an interview to Science Brian revealed he was patient 1, and his wife was patient 3.
The lucky person who was patient 2 was Brian’s PhD student Kevin Kobylinski, who had been collecting mosquitoes with him as part of his malaria research. Being bitten came with the job, so they were vaccinated against some of the major disease, including Dengue fever.
The symptoms, when they arrived, seemed to suggest they had nonetheless caught Dengue fever. Headaches, torso rashes and fatigue all round lasting for a week, then muscle pains which lingered longer. They sent blood samples to the U.S. Centers for Disease Control and Prevention, who ran a number of antibody tests. The tests showed that all three had antibodies against Zika virus, which infects monkeys and humans in Africa and Asia.
But Brian’s wife, Chilson, has never travelled to Africa or Asia. The cool climate of Colorado supports different mosquito species to those tropical varieties which spread Zika. In fact, Zika had never been recorded in the Western Hemisphere.
They concluded that Zika had been transmitted human to human, and probably sexually, as their four children didn’t get the disease.
If Zika virus can be spread by sexual transmission, it could change the way the disease is prevented. Zika is considered an emerging pathogen, having infected about 70% of the people on Yap Island in the Pacific during 2007.
Foy, B. (2011). Probable Non–Vector-borne Transmission of Zika Virus, Colorado, USA Emerging Infectious Diseases DOI: 10.3201/eid1705.101939 (pdf)