Spotlight on Zika Virus: An insect-borne STD?

Feb 5, 2014 | Katharina Schwan | Featured Series

Don’t be surprised if you’ve never heard of Zika virus. It’s a relatively unknown mosquito-borne infection that causes only mild illness and is barely distinguishable from other, better-known diseases such as dengue fever or West Nile. Prior to 2007, only 14 cases of the infection had ever been described in medical literature.

History of Zika Virus

The virus was first discovered in 1947 when a rhesus monkey living in the Zika forest in Uganda developed an unknown febrile illness. Scientists were able to isolate a new transmissible agent from the sick monkey, which was named Zika virus, or ZIKV. A year later, that same virus was found in the Aedes africanus mosquito, also captured in the Zika forest; thus, the vector of ZIKV was identified.

Interestingly, researchers did not find evidence of human infection with ZIKV until twenty years later when it was isolated from human patients in Nigeria. Similar results from studies conducted in other parts of Africa and Asia established ZIKV as endemic in that part of the world.

In the past decade, however, ZIKV spread beyond its usual geographic boundaries, causing outbreaks in some of the most remote regions of the world. In 2007, an outbreak of Zika virus was reported on the isolated Yap Island in the Federated States of Micronesia. Although the outbreak caused only mild illness among the 108 confirmed cases, researchers expressed concern about the potential for further spread of ZIKV to other islands in Oceania, and possibly even to the Americas.

This is precisely what happened.

Current Outbreaks

In January of this year the French Polynesia Department of Health confirmed outbreaks of Zika virus on at least 15 different islands, including popular vacation destinations Tahiti and Bora Bora. According to a report released by the European Center for Disease Prevention and Control (ECDC), the outbreak began in October 2013 and it is estimated that more than 27,000 patients sought medical care for symptoms congruent with ZIKV infection. Cases are also being reported from New Caledonia and from Japanese travellers returning from Bora Bora.

First ever mosquito-borne STD?

Yet, the most interesting case of ZIKV infection is that of the wife of Colorado-based malaria researcher, Brian Foy. Foy contracted the disease while conducting fieldwork in rural Senegal. After returning home from his trip, Foy felt feverish and tired, had swollen joints and a splitting headache. Nine days later, his wife Joy, who had not accompanied him to Senegal, also fell ill and presented similar symptoms. Their four children remained healthy.

Foy and his PhD student, Kevin Kobylinsky released a study in the May 2011 journal of Emerging Infectious Diseases, detailing this strange series of events. The two scientists provide evidence for what may be the first case of sexual transmission of an insect-borne disease.

The study states that both Foy and Kobylinsky were infected with ZIKV while working in southeastern Senegal from bites by the Aedes mosquito. Foy’s wife, however, could not have gotten the illness from the bite of a mosquito. She had not traveled outside of the United States since 2007 and ZIKV has never been reported in the Western Hemisphere. Additionally, the Aedes mosquito naturally exists in tropical climates and it is unlikely that it could survive in northern Colorado. Thus, the results support human-human transmission between Foy and his wife. Since the illness did not develop in the couple’s children, however, it is reasonable to suspect that ZIKV passed from one patient to another through direct contact with body fluids, which would be exchanged through intercourse or possibly, but less likely, through kissing.

Don’t worry, this does not mean that other, more severe, mosquito-borne illnesses like malaria or dengue can be transmitted through sexual contact. At this point in medical research, Foy’s experience presents only circumstantial evidence towards sexual transmission of ZIKV. Additionally, this is the first and only documented case of a “mosquito-borne STD” and there is no evidence of other arboviruses behaving similarly. 

What should you do?

If you’re traveling to a place where ZIKV is endemic or where outbreaks of ZIKV have been reported, including parts of Africa, Asia and the Western Pacific, the best thing to do is to protect yourself against mosquito bites. Be aware of the symptoms of Zika infection, which include: fever, conjunctivitis, joint pain and rash. There are no vaccines and no cure for ZIKV, but the symptoms are typically mild and the illness usually resolves itself within 4-7 days. 

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