Dangerous Mosquito-Borne Illness, Zika, Moves into Northern Hemisphere

By John Henry Dreyfuss, MDalert.com staff.
Save to PDF Primary CareInfection ControlObstetrics/Gynecology By
  • Zika infection is linked to microcephaly in children exposed in utero.
  • The virus is carried by Aedes aegypti mosquito.
  • Children with microcephaly are born, often, with incomplete brain development.
  • CDC warns pregnant women to avoid travel to 14 countries and territories where Zika is currently prevalent.
  • There is no vaccine against Zika infection and no treatment for the disease.

The Zika virus is endemic to equatorial zones around the planet. The virus has long been known to cause Zika fever as well as encephalitis. More recently, it has been linked to an epidemic of microcephaly among newborns whose mothers are infected during pregnancy.

According to an article in Wikipedia, Zika is a member of the Flavivirus genus in the family Flaviviridae. This genus includes the West Nile virus, dengue virus, the tick-borne encephalitis virus, yellow fever virus, and other viruses that can cause encephalitis. Zika fever and the Zika virus are named for the Zika Forest in Uganda where the virus was first isolated in 1947. There is no vaccine or treatment for Zika infection or Zika fever.

 

Figure 1. The Zika virus is transmitted by the Aedes aegypti mosquito.

Prevention

Given that Zika is typically transmitted by the Aedes aegypti mosquito (Figure 1, Figure 2), which is also known to carry the dengue, yellow fever, and Chikungunya viruses, physicians can advise patients to avoid areas where Zika fever is prevalent. In cases where patients must travel to such areas, physicians can suggest a number of techniques to avoid exposure to mosquitoes. These include the use of DEET-containing insect repellents, among others. The use of an insect repellent that contains a high concentration of DEET (N,N-diethyl-meta-toluamide) is an effective strategy. DEET-based repellents typically contain 4% to 100% DEET. The higher the concentration, the more effective the repellent.

 

Figure 2. A mosquito proboscis at high magnification.

Since its development by the U.S. Army in 1946, DEET has proven to be a highly effective insect repellent. However, there are significant health warnings associated with this chemical. Both physicians and patients should be aware of these. The Environmental Protection Agency (EPA) keeps a website dedicated to DEET. Click here for more information.

Other protective techniques include:

  • Cover exposed skin by wearing long-sleeved shirts and long pants.
  • Use an insect repellent containing one of the following active ingredients:
  • DEET
  • Picaridin
  • Oil of lemon eucalyptus (OLE) or PMD
  • IR3535
  • If your patient will use both sunscreen and an insect repellent, advise him or her to apply the sunscreen first, let it dry, and then apply the insect repellent.
  • Use permethrin-treated clothing and gear (such as boots, pants, socks, and tents). Patients can apply permethrin themselves or can purchase pre-treated products. (Materials treated with permethrin may remain protective after multiple washings. It is important to follow the product information to know how long the protection will last.)
  • If possible, travelers should stay and sleep in screened-in or air-conditioned rooms.
  • If sleeping while exposed to the outdoors the use of a dense bed net is advised.
 

Figure 3. The Zika virus.

The Current Zika Microcephaly Epidemic

While Zika fever has long been prevalent near the equator, 2015 saw cases of the disease further into the Northern Hemisphere. For instance, health officials in Hawaii believe that a baby recently born with microcephaly at an Oahu hospital was infected with the Zika virus (Figure 3) in utero.

In reporting the laboratory finding to the U.S. Centers for Disease Control and Prevention (CDC), the Hawaii state health department said the child’s mother probably had a Zika infection while living in Brazil in spring of 2015. Brazil is experiencing an outbreak of the mosquito-borne virus. Since October of 2015 more than 3,500 children have been born with microcephaly that is attributable to Zika infection. There have been at least 29 fatalities.

The U.S. Centers for Disease Control and Prevention recently advised pregnant women not to travel to countries and territories where local transmission of Zika has occurred. These include Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela, and Puerto Rico (Figure 4). The latest test results from Brazil have shown “increasingly strong evidence” of a link between the virus and fetal brain damage, according to the CDC.

The increasing prevalence of Zika fever and resulting microcephaly in Brazil has raised significant concerns. The country will host the 2016 Summer Olympics and hundreds of thousands of tourists will visit. Health experts are unsure why the virus has spread so rapidly in Brazil, but warn that large-scale tourism events may create an opportunity for the virus to multiply, perhaps mutate, and spread to other parts of the world.

 

Figure 4. International Zika virus prevalence.

Link with Microcephaly

Health officials studying the 2015 Brazilian outbreak suspect that the disease may cause microcephaly in babies born to infected women. However, there are very few such reports in the medical literature. As of November 2015, reports from the Brazilian Health Ministry suggested a connection between the Zika virus and cases of newborn microcephaly in Northeastern Brazil This alert was based on 2 cases of fetuses in whom amniocentesis confirmed the presence of the Zika virus. Ultrasound findings in these showed that both had microcephaly. One of the fetuses was also found to have intraocular calcifications and microphtalmia.

The Brazilian Ministry has confirmed the connection between Zika infection in pregnant women and microcephaly in newborns. Brazilian health officials have recommended that parents consider putting off pregnancy due to the sharp increase in cases of microcephaly.

On January 15, 2016 the U.S. CDC issued a Level-2 travel alert for people traveling to Zika-infected areas in Central and South America and the Caribbean, recommending that pregnant women in any trimester, and women who are trying to become pregnant, postpone travel to the affected areas.


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