Zika, an overview

Vector-borne diseases are one of the greatest contributors to human mortality and morbidity in tropical areas. Over the past two decades, vector-borne diseases have spread globally at an increased rate. This is mainly related to population movements, climate change, deforestation and rapid unplanned urbanization creating the perfect conditions for mosquitoes and the virus they carry to spread. Alongside this alarming spread of vectors is the serious concern of increasing insecticide resistance and the shortage of entomologist and vector-control experts.

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Zika is a vector-borne disease and the virus was first identified in 1947 from a rhesus monkey in the Zika forest in Uganda. It belongs to the flavivirus family, which also includes dengue, yellow fever, and West Nile virus. Originally confined to Africa, Zika started expanding to Asia in 2007. The first cases in the Americas were detected in Brazil in 2015 and since then the virus has spread exponentially. The numbers of new cases is declining, in most places the epidemic is over and the virus is likely to be endemic.

The virus is transmitted among humans by infected mosquitoes (Aedes mosquito) and sexual contact. We also know that mothers can pass the virus to their children either through transplacental transmission or during delivery.

Most of the people who contract Zika don’t even realize they have been infected, only 25% of infected people develop symptoms including rash, fever, joint pain, conjunctivitis and headache. Other serious health effects associated with Zika are birth defects and Guillain Barré.

The problem arises when the virus moves to a new geographical area and encounters a population that has never been infected before. Pregnant women are particularly at risk since the virus has the ability to cross the placenta and potentially cause permanent damage to the fetus brain leading to microcephaly. Other problems with in-utero infection include eye defects, hearing loss and impaired growth. Zika has also been associated with other adverse pregnancy outcomes including miscarriage and stillbirth.

Transmission of Zika virus to the fetus has been documented in all trimesters and a diagnosis of  Zika infection during any trimester may be associated with fetal or neonatal abnormalities including growth delays. Data analyzed from three birth defects surveillance programs demonstrated that the proportion of pregnancies with birth defects is approximately 20-fold higher, compared with the proportion seen before Zika was introduced into the region of the Americas in 2016. According to a CDC report 8% of offspring of pregnant women who tested positive for Zika in the first trimester, 5% in the second trimester and 4% in the third trimester had birth defects linked to the virus.

Based on current scientific evidence, once a person has been infected with Zika, he or she is likely to be protected from future Zika infection. There are currently no antiviral drugs or vaccines that can be used to treat or prevent infection with Zika virus.

Mosquito control is the only option for restricting Zika virus infection.

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Avoid mosquito bites and protective measures including EPA-approved bug spray with DEET, covering exposed skin, and staying indoors or screened-in areas.

Given the serious nature of birth defects associated with the virus it is prudent for pregnant women to either avoid travel to areas that are endemic for Zika or to take measures to reduce exposure to mosquitoes. Using condoms during sex or abstaining from sex for the duration of the pregnancy in areas with active Zika virus transmission is advised.

It is not just Zika we are fighting but a global change that is happening too fast for the natural world to adapt on its own. A global health agenda that gives priority to vector control could save many lives and prevent much suffering.

For more information about this topic and counseling to reduce risk of Zika during pregnancy contact Dr. Evelyn Zeda at 939-261-2222.

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