Zika Virus and the Eye

Knowledge about the potential effects is still evolving.

By Agustin L. Gonzales, OD, FAAO

In February, the director-general of the World Health Organization declared the cluster of cases of microcephaly and other neurologic disorders reported in Brazil to be a Public Health Emergency of International Concern.1 In that statement, the cluster was noted to be associated with infection with the Zika virus, with a “strongly suspected, though not scientifically proven,” causal relationship.1

Local transmission of the Zika virus has been confirmed in many countries and territories, with Brazil being the most recognizably affected country. With the advent of summer and mosquito season in the Northern Hemisphere, this arbovirus is expected to continue to quickly spread to other geographic locations. As of June 2016, there were a reported 756 travel-related cases of Zika virus infection in the continental United States.2

The spread of the virus is primarily attributed to the bite of infected mosquitoes, specifically Aedes aegypti and Aedes albopictus. The mosquitoes become infected when they bite an individual who has the Zika virus, and then they act as vectors, transmitting the virus to other individuals via the same mechanism. Transmission of the Zika virus among humans can also occur during sexual intercourse, through pregnancy, and likely through blood transfusion.3

From a primary care perspective, there is a diagnostic challenge, as the majority of infected individuals may remain asymptomatic or experience only mild symptoms associated with the infection. The most commonly observed symptoms are similar to those of any viral infection, including mild fever, joint pain, rash, and/or red eyes.3 However, recent developments have established that Zika virus infection poses a significant threat to fetal development in pregnant women.

After a period of caution regarding asserting a causal link, scientists at the US Centers for Disease Control and Prevention (CDC) recently announced that there is now enough evidence to conclude that Zika virus infection during pregnancy is a cause of microcephaly and other severe fetal brain defects.4

As we understand more about the virus, other notable defects have been recorded, including hearing deficits, impaired growth, and eye defects.4 Researchers have found a strong link between eye problems and Zika virus infection. A study of 29 Brazilian babies assumed to have congenitally acquired Zika virus found that about one-third of them had ophthalmic complications including optic nerve head abnormalities, ocular lesions, and chorioretinal atrophy.5

In another recent publication, researchers in Brazil and at Stanford University examined three Brazilian male infants with microcephaly born in late 2015. These children’s mothers were suspected to have acquired Zika virus during the first trimester of their pregnancies. These case studies documented several kinds of ocular problems not previously linked to Zika virus disease, some of which could cause visual impairment. Among the findings observed were increased cup-to-disk ratios, hypoplasia of the optic nerve, torpedo maculopathy, macular pigment mottling, chorioretinal atrophy, hemorrhagic retinopathy, lens subluxation, and iris coloboma.6

Unfortunately because of the recent discovery of the link between Zika virus and these abnormalities, the limited sample sizes of recent publications, and the fact that these are based on observational and case report data, it is difficult to use these studies as guides for public health initiatives, other than suggesting eye health screenings for affected infants. Researchers also recognize that it is not clear whether Zika virus itself has caused the eye development problems noted or whether they are secondary to microcephaly. Despite the fact that there is much more to be learned about this arbovirus, this information provides significant leads for clinicians to better intervene and understand the ophthalmic manifestations observed among Zika-infected children.

Determining the exact cause of these ophthalmic complications would significantly increase the accuracy of screening for affected children. For now, the important thing is to follow the screening recommendations of the CDC.7 These include subjecting all babies who are suspected to be affected by Zika virus to applicable examinations. Through this screening process, information will be obtained from this larger cohort, and appropriate agencies, such as the CDC, will soon be able to report a clearer picture about the viral infection and the defects it causes, and a better public health plan will emerge.

LATE-BREAKING NEWS

At press time, the Florida Department of Health had identified an area in one neighborhood of Miami where Zika is being spread by mosquitoes. The CDC issued an unprecedented travel warning, advising pregnant women and their partners not to travel to the community. According to agency spokesman Tom Skinner, this is the first time the CDC has warned people not to travel to an American neigborhood for fear of catching an infectious disease. A total of 15 people have been infected with Zika after being bitten by local mosquitoes.

CDC guidance was issued for people who live in or traveled to this area any time after June 15 (based on the earliest time symptoms can start and the maximum 2-week incubation period for Zika virus). See the full report here: http://www.cdc.gov/zika/intheus/florida-update.html. n

1. WHO Director-General summarizes the outcome of the Emergency Committee regarding clusters of microcephaly and Guillain-Barré syndrome. World Health Organization website. February 1, 2016. http://www.who.int/mediacentre/news/statements/2016/emergency-committee-zika-microcephaly/en. Accessed June 9, 2016.

2. Hennessey M, Fischer M, Staples JE. Zika virus spreads to new areas—Region of the Americas, May 2015-January 2016. MMWR Morb Mortal Wkly Rep. 2016;65(3):55-58.

3. Zika Virus. Centers for Disease Control and Prevention. www.cdc.gov/zika. Accessed June 9, 2016.

4. Zika and Pregnancy. Centers for Disease Control and Prevention. www.cdc.gov/zika/pregnancy/question-answers.html. Accessed June 9, 2016.

5. de Paula Freitas B, de Oliveira Dias JR, Prazeres J, et al. Ocular findings in infants with microcephaly associated with presumed Zika virus congenital infection in Salvador, Brazil. JAMA Ophthalmol. 2016;134(5):529-535.

6. Miranda HA 2nd, Costa MC, Frazão MA, et al. Expanded spectrum of congenital ocular findings in microcephaly with presumed Zika infection [published online ahead of print May 25, 2016]. Ophthalmology. 2016. doi: 10.1016/j.ophtha.2016.05.001.

7. Petersen EE, Polen KND, Meaney-Delman D, et al. Update: Interim Guidance for Health Care Providers Caring for Women of Reproductive Age with Possible Zika Virus Exposure—United States, 2016. MMWR Morb Mortal Wkly Rep. 2016;65(12):315-322. doi: 10.15585/mmwr.mm6512e2.

Agustin L. Gonzalez, OD, FAAO
• Optometric glaucoma specialist and therapeutic optometrist in practice at Eye & Vision in Richardson, Texas
ag@txeyedr.com

Screen All Pregnant Women

Comment from María H. Berrocal, MD

The Zika virus presents a significant threat to pregnant women. Although the virus causes a mild, often asymptomatic illness, its ability to cross the placenta and cause neural damage to the fetal brain presents a significant health challenge. It is estimated that 80% of infected individuals do not present any symptoms, and therefore, according to the Centers for Disease Control and Prevention, all pregnant women must be screened for the virus.1

Infection during the first trimester of pregnancy appears to cause the most neurologic damage, so early screening is important. The virus has been found in saliva, semen, breast milk, and urine so person-to-person transmission is an issue.

The virus can affect the retina and optic nerve even without causing microcephaly, and therefore all babies who are born Zika-positive should be screened ophthalmologically for findings with imaging.2

The Aedes aegypti mosquito, which is the vector of the virus, is present throughout the southern United States. Although no nontravel-related cases of Zika transmission have been reported in the continental United States at present, there are 234 women infected with Zika during their pregnancies in the contiguous US states, according to the CDC.3 With warmer weather expected in the summer months, it is plausible that the Zika virus may infect the Ae aegypti mosquito in the continental United States. Surveillance of all pregnant women should be carried out for early detection of the infection in fetuses.

1. Petersen EE, Polen KND, Meaney-Delman D, et al. Update: Interim Guidance for Health Care Providers Caring for Women of Reproductive Age with Possible Zika Virus Exposure—United States, 2016. MMWR Morb Mortal Wkly Rep. 2016;65(12):315-322. doi: 10.15585/mmwr.mm6512e2.

2. V entura CV, Maia M, Dias N, et al. Zika: neurological and ocular findings in infant without microcephaly. Lancet. 2016;387(10037): 2502. doi: 10.1016/S0140-6736(16)30776-0.

3. Tavernise S. CDC reports 234 pregnant women in US with Zika. New York Times. June 16, 2016. http://www.nytimes.com/2016/06/17/health/zika-pregnancy-united-states-cdc.html. Accessed July 7, 2016.

María H. Berrocal, MD
• Assistant professor, University of Puerto Rico School of Medicine, San Juan
• Member of the editorial board of Retina Today, sister publication of AOC
• (787) 725-9315; mariahberrocal@hotmail.com