Zika Virus: A Quick Update

Feb 1, 2016 | Yulin Hswen Colleen Nguyen | Outbreak News

In early December 2015, we reported on Brazil’s microcephaly outbreak and its alleged potential connection with Zika virus. This piece is a quick update to last month’s post, alongside some updated information.


The Spread of the Zika Virus

On Thursday, Jan 28, 2016, the World Health Organization (WHO) held a special meeting to discuss the potential spread of the Zika virus that may lead to 3-4 million cases in South, Central, and North America over the next 12 months [1, 2]. “The level of alarm is extremely high,” says Dr. Margaret Chan, the director general of the WHO because the virus is “spreading explosively” in the Americas. Widespread criticisms regarding how the WHO handled the last major global health crisis, Ebola, has prompted the WHO to convene another emergency meeting today, Monday February 1st, 2016 to decide if the Zika virus will be declared a public health emergency [3].

The suspected connections between the high number of infants being born with microcephaly (abnormally small, and underdeveloped, heads) in Brazil have “changed the risk profile of Zika from a mild threat to one of alarming proportions,” said Chan [1, 4]. Before the Zika outbreak, approximately 150 cases of microcephaly had been reported in 2014 and fewer than 200 in the five previous years had been reported in Brazil [5, 6]. Since October 2015, the number of infants born with microcephaly has risen to 4,180 [7] and it is estimated that Zika has affected between 440,000 and 1.3 million people in Brazil since its first confirmation last May. [8]

With the increasing rates of global travel, the virus first detected in May has spread to more than 23 countries in the Americas. At least 31 cases of the Zika virus have been imported into the U.S. and in early January 2016, the U.S. Centers for Disease Control and Prevention reported that an infant with microcephaly associated with Zika virus was born in Hawaii, the first in the U.S., after the mother had spent part of her pregnancy in Brazil [9]. Furthermore, Chan stated, “the El Niño pattern is expected to increase mosquito populations in many areas.” This may increase the number of cases in temperate parts of the U.S. as El Niño creates warmer, rainier summers that favor the survival of the Zika virus in mosquitoes, explained Dr. Oliver Brady of the University of Oxford [10, 11].


Historical Context and Epidemiology

Zika is a mosquito-borne flavivirus transmitted by Aedes genus mosquitoes – primarily the A. aegypti – which also transmits diseases such as chikungunya, dengue, and yellow fever [12]. While first identified in Ugandan rhesus macaques in 1947, the virus was not identified in humans until 1952 in Uganda and Tanzania [13]. Since its initial emergence, outbreaks of Zika virus and its serological (virus identification in blood) presence have been identified in Africa and Asia – and most recently, in countries across Latin America [13].

Signs and symptoms of Zika are mild and last approximately two to seven days; they include fever, conjunctivitis, malaise, muscle and joint pains, headaches, and skin rashes [12]. According to the WHO, Zika outbreaks in French Polynesia and Brazil in 2013 and 2015 respectively, first cited potential auto-immune and neurological issues [12]. Diagnosing Zika through serology can be complicated, as Zika often cross-reacts with viruses from the same Flavivridae family such as dengue, yellow fever, and West Nile virus[12]. 

A vaccine for Zika does not currently exist. As a result, prevention is  the best means for which to control infection and spread of the virus. Prevention of Zika virus primarily encompasses mosquito vector control, including the removal and reduction of breeding sites [12]. Control also includes reducing contact between people and mosquitoes, which can be done by wearing light colored clothes, covering up the body as much as possible, as well as the application of mosquito repellent, and utilization of physical barriers such as mosquito nets, screens, doors, and windows [12].


Microcephaly and Other Neurological Issues

In an interview with NPR, Dr. Joao Ricardo de Almeida, a member of Brazil’s investigation team, notes that brain scans of babies born with suspected Zika-linked microcephaly have “profound abnormalities” and that they are “notably different than scans of other babies born with the same defect” [14]. The degree of damage caused by microcephaly means that these infants “are not going to be functional” and will “need care for the rest of their lives” says Ricardo de Almeida [14]. Along with microcephaly, additional effects noted through Zika-linked cases seem to be only be “the tip of the iceberg” says Dr. Albert Ko from Yale University since even children who appear healthy – with normal sized heads - may experience other neurological problems and future developmental delays [14].

Finally, there have also been reports that Zika virus may be connected to the autoimmune disorder Guillain Barré, which causes “ascending motor paralysis” and “interferes with the ability of nerves to function and survive” says Dr. Bruce Hirsch, an infectious disease specialist at North Shore University Hospital, in Manhasset, New York. Although this is a just an association at this point, more data is needed to prove a cause and effect, says Dr. Lee Norman, chief medical officer at the University of Kanas Hospital [9].



The alarming increase in birth defects, and possible paralysis, linked to the Zika virus has prompted drastic warnings to be issued by El Salvador health officials, who have advised all women of the reproductive age to delay pregnancy for two years, until 2018. Other countries like Colombia and Ecuador have also released the same advisory statement and advised women to avoid getting pregnant until more information has become available [15, 16].

The C.D.C. has advised pregnant Americans or women planning to become pregnant to avoid travel to these affected areas:

The Commonwealth of Puerto Rico, a U.S. territory; Barbados; Bolivia; Brazil; Cape Verde; Colombia; Ecuador; El Salvador; French Guiana; Guadeloupe; Guatemala; Guyana; Haiti; Honduras; Martinique; Mexico; Panama; Paraguay; Saint Martin; Samoa; Suriname; Venezuela, United States Virgin Islands and Dominican Republic. [17] 





1.            Zika "spreading explosively," global health experts warn, in CBSNEWS. 2016: CBSNEWS.

2.            Lindmerier, C. WHO to convene an International Health Regulations Emergency Committee on Zika virus and observed increase in neurological disorders and neonatal malformations. 2016; Available from: http://www.who.int/mediacentre/news/statements/2016/emergency-committee-zika/en/.

3.            Tavernise, S., Zika Virus ‘Spreading Explosively’ in Americas, W.H.O. Says, in New York Times. 2016: New York Times.

4.            Marcus, M.B., Zika virus raises new worry about paralysis, in CBSNEWS. 2016.

5.            The spread of Zika virus, in The Economist. 2016.

6.            Jr, D.G.M., Hawaii Baby With Brain Damage Is First U.S. Case Tied to Zika Virus, in New York Times. 2016.

7.            Romero, S., Reports of Zika-Linked Birth Defect Rise in Brazil, in New York Times. 2016.

8.            Welch, A., What you need to know about Zika virus, in CBSNEWS. 2016.

9.            Hawaii baby born with brain damage linked to Zika virus, in CBSNEWS. 2016.

10.          Cognlan, A., 4 million at risk of Zika infection as El Niño increases spread. 2016.

11.          Bogoch, I.I., et al., Anticipating the international spread of Zika virus from Brazil. The Lancet, 2016.

12.          Zika Virus: Fact Sheet. 2016  [cited 2016 Jan 31]; Available from: http://www.who.int/mediacentre/factsheets/zika/en/.

13.          Hayes, E.B., Zika virus outside Africa. Emerg Infect Dis, 2009. 15(9): p. 1347-1350.

14.          Garcia-Navarro, L., Zika-Linked Brain Damage in Infants May be ‘Tip of the Iceberg’, in NPR. 2016.

15.          Ahmed, A., El Salvador’s Advice on Zika Virus: Don’t Have Babies. 2016.

16.          Mohney, G., El Salvador Advises Women to Avoid Pregnancy for 2 years Due to Zika Virus Outbreak. 2016.

17.          CDC adds 2 destinations to interim travel guidance related to Zika virus. Media Statement 2016  [cited 2016 Jan 26]; Available from: http://www.cdc.gov/media/releases/2016/s0126-zika-travel-guidance.html.

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