Zika Virus – Severity & Extent of Outbreak

Origin of the Outbreak

The current Zika outbreak can be traced to Brazil. Brazil’s National Reference Laboratory confirmed the first cases of Zika in May of 2015. Unconfirmed cases in the country date back nearly two months prior, in late March.

Map showing geographic spread of current Zika epidemic (CDC, 2016). 

State of the Outbreak

Originating in Brazil, Zika virus has since made its way through nearly every country of South America and the Caribbean, reaching as far north as Mexico and the southern United States. As of yesterday, October 12^th, Zika cases (people infected with Zika) in the U.S. totaled to 3,936 (up by 100 compared to last week). On the plus side, most of these were travel-related cases. Locally acquired cases remain much lower (128 cases) and have occurred only in Florida (Miami-Dade County). What does this mean? It means while Zika has touched all 50 states, people are still only “getting” Zika elsewhere. The exception is for sexual transmission, which is responsible for less than 1% of total cases thus far. Other countries with reported Zika outbreaks include several countries in Oceania and the Pacific Islands, and a single country in Africa (Cape Verde) and Asia (Singapore). The U.S. Centers for Disease Control and Prevention has issued travel notices for these areas, including special guidance for those traveling to south Florida.

Pregnant Women with Zika

Currently in the U.S. there have been 878 pregnant woman reported with “any laboratory evidence of possible” Zika infection, according to the U.S. Centers for Disease Control and Prevention. Yes, this number is astonishingly high given total U.S. cases. But keep in mind, these are “possible” infections. The number is likely inflated by a high number of mothers visiting hospitals and the inherent delay before tests can be confirmed. Perhaps more noteworthy are the 23 babies with confirmed birth defects. This number reflects birth defects among live newborns in the U.S. infected with Zika either before or during birth. Because we don’t know how many infected newborns do NOT have Zika, we can’t identify the true rate of birth defects. But we can get a crude idea of birth defects per “possible” infected pregnancy, which comes to just over 2.5%—a low proportion at least!

Keep in mind there remains no vaccine for Zika, so if you’re pregnant or otherwise want to reduce your risk of contracting Zika virus, heed the travel warnings mentioned above!  

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                                                         Dr. Shahir Masri

                                                         Environmental Health Scientist