Zika fever

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at February 5, 2016
StartDiseasesZika fever

Despite being around for over 60 years, the Zika virus has only recently spread globally and attracted international media attention. Zika fever or Zika virus disease has reached pandemic levels, and the World Health Organization has declared it an international public health emergency. As many as four million people could be infected by the end of 2016.

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Definition & Facts

Zika virus, the cause of Zika fever, is related to the viruses that cause dengue fever, West Nile fever, and yellow fever. It was first isolated in 1947, and, until 2015, was not considered a serious threat. About 1 in 5 people who are infected with the Zika virus will develop Zika fever, and the symptoms are usually mild. The virus only recently spread out of the forests of Africa, showing up in the Americas in 2015.

Symptoms & Complaints

Like the diseases caused by several other exotic viruses, the most common symptoms of Zika fever are fever, joint pain, rash, and conjunctivitis (red eyes). Symptoms can also include muscle pain and headache. Zika fever is self-limiting, and symptoms usually last a few days to a week.

Zika virus can pass from pregnant women to newborns, and has potentially been linked to microcephaly in the infant. Microcephaly is a neurodevelopmental disorder characterized by smaller than average head size. Infants with microcephaly usually have neurological defects, seizures, impaired development, and possibly impaired motor skills. Zika’s link to microcephaly has not been proven however, as it only surfaced in Brazil in 2015, and has not shown up in other countries that have a Zika virus presence.

Zika virus has also been potentially linked to neurological disorders in adults, such as Guillain-Barré syndrome (GBS). GBS is when a person’s own immune system starts attacking the nerve cells, causing muscle weakness and, in severe cases, paralysis. GBS is not very well understood, and the potential link between GBS and Zika fever is still being studied.

Causes

Due to how recently Zika has received public attention, not much is known for sure about how it is transmitted, or what the risk of disease is by the various transmission methods. Zika’s natural carriers are primarily monkeys. Mosquitoes are the vector that transfer the virus from monkey to human, or from human to human.

The specific species that carry Zika virus (Aedes aegypti and A. albopictus) are found worldwide, and also spread dengue virus and chikungunya virus. After a mosquito picks up the Zika virus, either from an infected monkey or a human, the virus must incubate for about 10 days before it can be passed on.

There are rare examples of Zika virus being sexually transmitted. So far, only two cases have been documented by the American Centers for Disease Control and Prevention (CDC): one in 2009, and one in 2016. How this works or how often it can occur is not known. The virus has also been transmitted through blood transfusion, but rates and risk are unknown.

The virus can also be passed from mother to child, although the effects aren’t known yet and its occurrence is rare. An infected mother can pass the virus on to the newborn during delivery, or the virus can possibly transfer into the placenta during pregnancy. The Zika virus has been detected in amniotic fluid twice, although the effect on the newborns wasn’t reported.

Diagnosis & Tests

Because Zika has symptoms similar to several other exotic viruses, and is usually found in the same regions of the world, medical and travel history aren't enough for a doctor to diagnose Zika fever. Blood tests can be used to test for Zika virus, but at this point, the tests can only be run at the CDC labs and a few state health departments, and have a turnaround time of up to two weeks.

During the first week of symptoms, Zika virus can be detected by polymerase chain reaction in serum or urine. The form of PCR used (reverse transcription PCR) amplifies and detects the virus’ genetic material.

After the first week of symptoms, another option is to perform serologies. Serology testing looks for antibodies the human body produces in response to infection. Serological testing is also useful for tracking the virus as it spreads around the world.

Treatment & Therapy

There is currently no antiviral drug that can treat Zika infections. The symptoms are minor, and only very rarely require hospitalization. Because there is no specific treatment, the only thing that can be done, either at home or in the hospital, is to treat the symptoms:

  • Get plenty of rest.
  • Drink fluids to prevent dehydration during the fever.
  • If necessary, relieve fever and pain with over-the-counter acetaminophen. Do not take aspirin, or other anti-inflammatory drugs as they could cause hemorrhage if the virus is actually dengue.

Because the Zika virus can be found in the blood during the first week of infection, extra caution should be taken to prevent exposure to mosquitoes to avoid the spread of the virus.

Prevention & Prophylaxis

There is no vaccine available for Zika virus, and the only way to prevent Zika infection is to avoid mosquito bites:

  • Cover any exposed skin with long-sleeved shirts and pants.
  • Stay in places that have air conditioning or use screen doors.
  • If sleeping outside or in a space exposed to the outside, sleep under a mosquito bed net.
  • Use insect repellent. (Do not use insect repellent on newborns).
  • Dress babies and children in long sleeves and pants, and cover cribs or strollers with mosquito netting.
  • Treat clothing with permethrin (an insecticide and repellent).

These are the same steps that should be taken during the first week of Zika infection, to avoid spreading the virus to other people.