By Femi Olawuyi
A recent concern with the Zika virus is the possibility of sexual transmission. As noted in recent posts, Zika virus is a mosquito-borne arbovirus disease transmitted by the same mosquito species (Aedes mosquitoes) that carry dengue disease. Although the disease can affect anyone, it has the potential to affect the unborn fetus and lead to microcephaly, a neurodevelopmental disorder. Zika virus was confirmed in the semen of an infected patient in Tahiti in 2013, and major United States and global health organizations, such as the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO), continue to monitor the sexual transmission possibility.
If the rare cases of sexual transmission of the disease become more common, then Zika virus may inevitably become a top global disease with double possibility of spreading: through mosquito bites (primary) and sexual contact (secondary). Also, this will put the disease into the sexual transmission infection (STI) class; another global STI may be inevitable if it is not contained. Zika virus becoming another major STI would change its diagnosis and treatment as well. The treatment would go beyond the flu-like vaccine that is currently sought after for primary non-sexual contact transmission through mosquito bites. A typical viral STI would require serum, blood plasma, vaginal fluid, and semen samples for diagnostic isolation and detection of the Zika virus.
Most STIs are caused by bacterial agents. For example, syphilis is caused by Treponema pallidum, Gonorrhea is caused by Neisseria gonorrhoeae, and chlamydia is caused by Chlamydia trachomatis. Although there are vaccines against some of the bacterial STIs, prescribed antibiotics are usually used to treat them. On the other hand, viral STIs—like Zika virus would be, if determined to be an STI—are caused by viruses. Examples are hepatitis A, B, C, D, and E, human immunodeficiency virus (HIV), and the human papillomaviruses (HPV). Viral STIs tend to be more difficult than bacterial STIs in terms of prophylactic and diagnostic treatment, and they pose more dangerous health impacts. For instance, HPV is connected with cervical cancer and genital warts; HIV is connected with acquired immune deficiency syndrome (AIDS) and other secondary immune diseases; and hepatitis A, B, C, D, and E are connected to liver disease. And now Zika virus is linked to microcephaly.
If research validates Zika virus as a sexually transmitted infection, the world would be dealing with a new viral STI, and the spread of the disease will be increased globally. For instance, more than 70 million people are infected with a viral STI like HPV. Annually, an estimated 20 million people acquire an STI, among which half are young people (15–24 years).
The availability of viral STI treatment for Zika virus will be another concern if its sexual transmission is fully confirmed. A typical viral STI poses serious challenges for pharmaceutical companies in terms of a cost effective and potent vaccine because of viral strain diversity and/or mutation. Good examples of STI vaccines with viral strain diversity are Merck’s Gardasil (HPV4) vaccine against four HPV types, FDA-approved GlaxoSmithKline’s Cervarix (HPV2) vaccine against two HPV strains, and the FDA-approved Merck’s HPV 9-valent vaccine.
Currently, Zika virus strains are based on geographical diversity. Zika strains originated from African (one strain in East Africa and three strains in West Africa) and Asian regions (Yap Island, Federated States of Micronesia), before the new strain in South America (predominantly in Brazil), which may be a mutated strain. Dealing with sexually transmitted Zika virus may require more than one vaccine if its mutation is more diversified.
While further investigation continues on the potential sexual transmission of the Zika virus, it will be important to report suspected cases and abstain from unsafe sexual practices.