A Young Woman Contemplating Travel Abroad: What She Needs to Know About Zika Virus Infection

AUTHOR:
Ronald Rubin, MD—Series Editor

CITATION:
Rubin R. A young woman contemplating travel abroad: what she needs to know about zika virus infection. Consultant. 2016;56(11):1024-1025.

A 22-year-old woman presents to your office for an informational visit. She is well and without specific health complaints, but she has questions that she needs and wants answered by a physician.

She is about to begin her senior year of college and has signed up for a semester away in Central America to fulfill elective credits. She has read and heard about the emerging epidemics and sporadic cases of Zika virus infections in that part of the world and even in the United States, and now she has second thoughts about going. She presents today to hear the known facts and risks from a health care professional and how they might relate to her own situation.

She is a healthy young woman with no chronic conditions such as diabetes mellitus. She is sexually active and uses oral contraceptives. 

Her vaccinations are up to date, except she is aware that she will need to receive the yellow fever vaccine before leaving for Central America.

Which of the following is NOT a correct statement about this young woman’s potential risk of Zika virus infection?

1. The most common syndrome associated with Zika infection is Guillain-Barré syndrome.
2. The potential for sexual transmission of Zika has been confirmed, but at this time mosquito-borne infection is most common.
3. An acute febrile illness with similarities to dengue is the typical initial manifestation of Zika infection.
4. No Zika virus vaccine is available at this time.

Answer and discussion on next page.

Answer: Statement A is not a correct statement about Zika virus.

One need only read a current newspaper or listen to a newscast to be aware of the recently described and still evolving Zika virus alarm in the world today. Although the Zika virus has been known to infect humans for more than 50 years based on serologic surveys, its spread and morbidity potential has recently increased exponentially.

Zika Virus Transmission

Like the dengue virus, the Zika virus is a flavivirus and for the most part is spread by a variety of mosquitos. It had been considered simply another tropical mosquito-borne viral illness. However, as our world continues to shrink and the global climate seems to be warming, subtle epidemiologic shifts are occurring that are increasing the infection rate and the geographic range of the Zika virus. Specifically, in classical endemic areas such as Africa and Southeast Asia, Zika had been most frequently confined to a sylvatic transmission cycle, with infection of nonhuman primates by forest- and tree-dwelling Aedes mosquitoes.

However, with the urbanization of the world, sporadic infection in humans now results in the virus more frequently entering urban and suburban higher-density population areas and subsequently sustaining increased spread, because in these areas the Aedes aegypti mosquito becomes the transmission vector. A aegypti is a dangerous and difficult vector of disease transmission, because it feeds primarily on humans, it is a relatively widely distributed “urban mosquito” rather than a forest or tree dweller, and it is a daytime feeder that is capable of multiple bites in a single blood meal.¹ In other words A aegypti is a high-efficiency vector for human transmission, and where these mosquitoes exist in significant number (eg, South Florida, where cases and mini-epidemics have already been found), Zika virus infection will follow.

In addition, it appears that once Zika establishes itself in an area, nonmosquito transmission also can occur. The most feared and well known is mother-to-fetus transmission, which has the potential for catastrophic neurologic defects.² But sexual transmission also has been reported and described,^1,3 and although it has not yet been reported, Zika virus transmission via blood transfusion seems very likely, since other flaviviruses can be transmitted this way.^1,3 At present, however, the incidence of sexual transmission remains far less common than mosquito-borne transmission, making Answer B a correct statement.

Presentation of Zika Infection

The clinical aspects of the Zika virus also are becoming established. The most common illness associated with Zika infection is an acute febrile illness, characterized by fever, a maculopapular rash, myalgia/arthralgia, and headache, that is qualitatively similar to if not as severe as that of dengue infection. Serologic surveys suggest that of 100 people infected, roughly 20% to 25% will develop such a syndrome (with the remainder never becoming symptomatic), and this is far and away the most common clinical manifestation. Therefore, Answer C is a correct statement. Guillain-Barré syndrome has been a documented complication of Zika infection, but it is uncommon, with estimates of approximately 1 in 1000 cases, which makes Answer A the incorrect statement.

Zika infection clearly causes profound fetal malformations, with microcephaly being the most common and well described. These malformations are the result of the vertical transmission of infection from mother to fetus, with the most risk seemingly occurring in the first trimester.^1,2,4 As of this writing, the best data indicate that Zika is capable of causing fetal abnormalities in some 29% of women infected during pregnancy—a stunningly high number.⁵

As of now there is no Zika vaccine, either live virus or passive antibody, so prevention in this manner is not yet possible, making Answer D a correct statement. The available prevention maneuvers currently are aggressive public health measures to lower the number of vector mosquitoes (eg, spraying) and to limit or avoid mosquito bites (eg, repellent, bed netting, window screens, air conditioning). The morbidity associated with infection during pregnancy surely must and will result in resource allocation toward all these schemes, as well as research of and progress toward an effective vaccine.

Patient Follow-Up

The young woman presented above will need to do detailed research about precisely where her coursework will be and the associated logistics and public health measures required therein—for example, what the living quarters will be regarding air conditioning and mosquito-control measures. She will need to make an educated decision about going or not depending on those findings.

Ronald Rubin, MD, is a professor of medicine at the Temple University School of Medicine and is chief of clinical hematology in the Department of Medicine at Temple University Hospital in Philadelphia, Pennsylvania.

References:

1. Peterson LR, Jamieson DJ, Powers AM, Honein MA. Zika virus. N Engl J Med. 2016;374(16):1552-1563.
2. Mlakar J, Korva M, Tul N, et al. Zika virus associated with microcephaly. N Engl J Med. 2016;374(10):951-958.
3. Pennsylvania Department of Health. Zika virus testing guidance. http://www.health.pa.gov/My%20Health/Diseases%20and%20Conditions/U-Z/Zikavirus/Documents/2016-PAHAN-353-9-09-Zika%20Virus%20Guidance%20Combined.pdf. Updated September 7, 2016. Accessed October 11, 2016.
4. Costa F, Sarno M, Khouri R, et al. Emergence of congenital Zika syndrome: viewpoint from the front lines. Ann Intern Med. 2016;164(10):689-691.
5. Brasil P, Pereira JP Jr, Raja Gabaglia C, et al. Zika virus infection in pregnant women in Rio de Janeiro—preliminary report [published online March 4, 2016]. N Engl J Med. doi:10.1056/NEJMoa1602412.