Zika: The Expanding and Deepening Threat

Marc Gozlan, MD


November 14, 2016

July 2016

July 1-15, 2016. On July 1, Guinea-Bissau confirmed its first three cases of the Zika virus. It was the latest country to report mosquito-borne Zika virus transmission. In total, 62 countries and territories had reported evidence of vector-borne Zika virus transmission since 2015.[82]

At the same time, Spain was the latest country to report Zika infection through sexual transmission. As of July 6, 2016, microcephaly and other CNS malformations potentially associated with Zika virus infection or suggestive of congenital infection had been reported by 13 countries or territories. At this date, the CDC had reported seven live-born infants with birth defects and five pregnancy losses with birth defects with laboratory evidence of possible Zika virus infection.[82]

As of July 13, 2016, Texas reported its first baby born with Zika-caused microcephaly—the fourth such case to be announced in a US state. The child's mother had traveled from Latin America, where she probably acquired the virus.

As it became clear that the Zika virus could be transmitted not only by mosquitos but also sexually, a report seemed to confirm bidirectional transmission. Indeed, on July 15, 2016, the CDC reported the first known case of female-to-male sexual transmission of Zika virus in a couple from New York City.[83] The woman had returned to New York City from an area with ongoing Zika virus transmission and engaged in a single event of condomless vaginal intercourse with her nontraveling partner. The woman was probably viremic at the time of sexual intercourse because her serum, collected 3 days later, had evidence of Zika virus RNA. The virus was present in either vaginal fluids or menstrual blood.[83]

Until this date, 11 countries (Argentina, Canada, Chile, Peru, United States, France, Germany, Italy, Portugal, Spain, and New Zealand) had reported evidence of person-to-person transmission of Zika virus, probably through sexual routes.[84]

Mid- to late July 2016. The presence of Zika virus in the genital tract of a woman with Zika virus infection identified in Guadeloupe was reported, suggesting potential risk for female-to-male transmission.[85] This patient was monitored for oocyte cryopreservation. On day 11 after the onset of symptoms, her blood and urinary samples tested negative, whereas her cervical mucous was found to be positive for Zika virus RNA. It was the first time that the presence of Zika virus was reported in the genital tract of an infected woman.[85]

On July 22, 2016, New York City reported the first baby born with Zika-related microcephaly in a local hospital. On July 25, 2016, the CDC updated guidance for healthcare providers caring for pregnant women with possible exposure to Zika virus.[86] This updated sexual transmission guidance was based on new information indicating that some infected pregnant women can have evidence of Zika viremia for longer than the previously recommended 7-day window for testing blood by RT-PCR after symptoms began, and that even pregnant women without symptoms can have viremia and viruria.

Therefore, the updated guidance expanded the Zika-specific blood testing for a longer period—up to 14 days—in pregnant women with symptoms and advised that pregnant women with possible Zika exposure but no symptoms receive this testing as well. The expanded guidance was also based on the recently reported case of female-to-male sexual transmission in New York City and preliminary data showing that Zika virus RNA can be detected in vaginal secretions. It expanded CDC's definition of sexual exposure to Zika to include sex without a barrier method (including male or female condoms, among other methods) with any person—male or female—who has traveled to or lives in an area with Zika.[86]

On July 27, 2016, Florida reported 328 travel-related Zika cases and 53 infections in pregnant women. The Florida health department investigated two cases of possible local Zika virus transmission. Investigations were conducted in Miami-Dade and Broward counties.

Two days later, on July 29, 2016, Florida confirmed the first local spread of the Zika virus through infected mosquitoes in the continental United States. Four locally acquired Zika cases were reported in two counties in Florida.[87] On August 1, 2016, an additional 10 cases were reported by Florida, bringing the total number of locally transmitted Zika cases in that state to 14.[88]

At the same time, the CDC noted on its website that microcephaly (Figure 6) had been linked to seizures; intellectual disability; hearing loss; vision problems; developmental delay, such as problems with speech or being able to sit, stand, and walk; and feeding problems, such as difficulty swallowing.

Figure 6. Microcephaly. Courtesy of the Centers for Disease Control and Prevention.

In other developments, the number of Zika infections in Puerto Rico had continued to rise since it was first detected in November 2015. The CDC reported that among symptomatic males and nonpregnant females who were tested, the percentage of persons with confirmed or presumptive Zika virus infection increased fourfold from 14% in February to 64% in June; during the same time, the percentage of persons with confirmed or presumptive Zika virus infection among symptomatic pregnant women increased fourfold, from 8% to 41%.[89] Also, the percentage of blood donation specimens testing positive had increased, with the highest percentage (1.8%) occurring in early July 2016.[89]


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