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Zika Virus

Understanding Zika Virus

Discovered in the Zika Forest of Uganda in 1947, the mosquito-borne Zika virus has very recently become a public health concern in the United States and throughout Latin America and the Caribbean. NIH MedlinePlus magazine spoke about Zika with Dr. Anthony S. Fauci, director of the NIH National Institute of Allergy and Infectious Diseases (NIAID).

Dr. Anthony S. Fauci, director of the NIH National Institute of Allergy and Infectious Diseases (NIAID)
Photo courtesy of NIAID

What does the American public need to know about Zika virus?

It is a bit complicated because as a disease—excluding the presentation in pregnant women—Zika is relatively mild. It is characterized by a few days or a week of aches, pains, fever, rash, and inflamed eyes—called conjunctivitis. The majority of people do not show symptoms.

Zika is a flavivirus, part of the same family of viruses that cause yellow fever and dengue fever. Aedes mosquitoes spread all three viruses. In terms of severity, yellow fever and dengue fever are deemed more serious than Zika.

What about the Zika virus and pregnant women?

If you are a pregnant woman and get infected with Zika during pregnancy, there is a chance—perhaps as high as one in three—that your fetus will have a congenital abnormality. The virus can cause microcephaly, a condition in which the fetus’s head is abnormally small and can be associated with incomplete brain development and destruction of brain cells. We are also seeing other Zika-associated fetal developmental problems such as eye defects, hearing loss, and impaired growth.

What risks does Zika pose for average Americans?

I use the analogy of the relative risk of those who frequently, or daily, drive on the Washington, D.C., Beltway, where serious accidents happen every day. That kind of accident happening to you is much more likely than getting infected in this area by some of the diseases people are concerned about, like dengue fever, chikungunya, or Zika.

By June 8, the Centers for Disease Control and Prevention (CDC) had identified Zika cases in 46 states. So far, none of these infections was acquired locally through infected mosquitoes. So far, all of these cases have been acquired through travel (or sexual contact with someone who has traveled) to countries or territories where Zika is circulating. In the continental U.S., it is almost certain that mosquito bites will spread Zika virus—but I do not expect we will see widespread or sustained outbreaks.

Are there other Zika-related conditions?

There are some other conditions that have been associated with Zika infection. One is Guillain-Barr syndrome (GBS), which occurs following an infection (like Zika) in the neurological system. The peripheral nerves (those nerves outside the brain and spinal cord) become diminished and can lead to severe neurological problems. Most people fully recover from GBS, although recovery can be lengthy. In very rare cases GBS results in permanent paralysis or death; NIH is gathering information to determine the percentage of people with Zika infection who develop GBS.

What institute is covering the research on Zika virus?

NIAID is predominately the institute involved with supporting the development of a Zika vaccine, but other institutes such as NICHD and NINDS are also researching aspects of the disease. At NIAID, we have decades of experience in developing vaccines for many types of infections, including those that fall in the same family as Zika, namely yellow fever, dengue, and West Nile virus. Vaccine development is something that ranks among our highest priorities and responsibilities.

What is NIAID’s timetable for developing a vaccine?

Likely in September, NIAID will begin a Phase I vaccine trial to determine whether the experimental vaccine is a safe vaccine and induces the predicted protective response. The trial will likely enroll about 80 people and take about four months for preliminary results. By the first quarter of 2017, NIAID could begin a much larger safety and efficacy trial to see if the vaccine can prevent disease.

The amount of time needed to determine efficacy will depend on the infection rate of the location where we test the vaccine. We could know as early as the beginning of 2018, but it may take much longer. Nonetheless, we are moving ahead expeditiously on the vaccine.

Any additional thoughts?

In collaboration with the Eunice Kennedy Shriver National Institute of Child Health and Human Development, we're conducting the Zika in Infancy and Pregnancy Study—referred to as ZIP. We're doing a lot of basic work to determine the natural history of the condition and associated congenital abnormalities, particularly microcephaly.

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Read More "Zika Virus" Articles

Understanding Zika Virus / Know Before You Go

Summer 2016 Issue: Volume 11 Number 2 Page 2-3