Zika virus was first discovered in the Zika forest of Uganda in 1947 in rhesus monkeys, but was not identified in humans until 1952 in Tanzania.[18]Smithburn KC. Neutralizing antibodies against certain recently isolated viruses in the sera of human beings residing in East Africa. J Immunol. 1952 Aug;69(2):223-34.
http://www.ncbi.nlm.nih.gov/pubmed/14946416?tool=bestpractice.com
[19]Dick GW, Kitchen SF, Haddow AJ. Zika virus. I. Isolations and serological specificity. Trans R Soc Trop Med Hyg. 1952 Sep;46(5):509-20.
http://www.ncbi.nlm.nih.gov/pubmed/12995440?tool=bestpractice.com
Since then, outbreaks have occurred sporadically in Africa, the Americas, Asia, and the Pacific. Until 2007, only 14 cases had been documented in humans worldwide.[20]Filipe AR, Martins CM, Rocha H. Laboratory infection with Zika virus after vaccination against yellow fever. Arch Gesamte Virusforsch. 1973;43(4):315-9.
http://www.ncbi.nlm.nih.gov/pubmed/4799154?tool=bestpractice.com
The first large outbreak was reported on the island of Yap (Federated States of Micronesia) in 2007.[21]Oehler E, Watrin L, Larre P, et al. Zika virus infection complicated by Guillain-Barre syndrome - case report, French Polynesia, December 2013. Euro Surveill. 2014 Mar 6;19(9). pii: 20720.
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20720
http://www.ncbi.nlm.nih.gov/pubmed/24626205?tool=bestpractice.com
[22]Duffy MR, Chen TH, Hancock WT, et al. Zika virus outbreak on Yap Island, Federated States of Micronesia. N Engl J Med. 2009 Jun 11;360(24):2536-43.
http://www.nejm.org/doi/full/10.1056/NEJMoa0805715#t=article
http://www.ncbi.nlm.nih.gov/pubmed/19516034?tool=bestpractice.com
The most likely source of this outbreak was introduction of the virus by travel or trade involving an infected person or an infected mosquito.[1]Kindhauser MK, Allen T, Frank V, et al. Zika: the origin and spread of a mosquito-borne virus. Bull World Health Organ. 2016 Sep 1; 94(9): 675–686C.
http://www.who.int/bulletin/volumes/94/9/16-171082-ab/en/
http://www.ncbi.nlm.nih.gov/pubmed/27708473?tool=bestpractice.com
Another large outbreak was seen in the Pacific Islands (French Polynesia, Easter Island, the Cook Islands, New Caledonia) in 2013 to 2014. This was the first outbreak where congenital malformations (e.g., microcephaly) and neurologic complications, including Guillain-Barre syndrome (GBS), were linked to the infection, although this association was made retrospectively.[21]Oehler E, Watrin L, Larre P, et al. Zika virus infection complicated by Guillain-Barre syndrome - case report, French Polynesia, December 2013. Euro Surveill. 2014 Mar 6;19(9). pii: 20720.
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20720
http://www.ncbi.nlm.nih.gov/pubmed/24626205?tool=bestpractice.com
[23]Cauchemez S, Besnard M, Bompard P, et al. Association between Zika virus and microcephaly in French Polynesia, 2013-15: a retrospective study. Lancet. 2016 May 21;387(10033):2125-32.
http://www.ncbi.nlm.nih.gov/pubmed/26993883?tool=bestpractice.com
[24]Cao-Lormeau VM, Blake A, Mons S, et al. Guillain-Barré syndrome outbreak associated with Zika virus infection in French Polynesia: a case-control study. Lancet. 2016 Apr 9;387(10027):1531-39.
http://www.ncbi.nlm.nih.gov/pubmed/26948433?tool=bestpractice.com
In the current outbreak, the first reports of locally transmitted infection came from Brazil in May 2015, although there are data to suggest that the virus originated in the Americas in Brazil between October 2012 and May 2013.[25]Ayllón T, Campos RM, Brasil P, et al. Early evidence for Zika virus circulation among Aedes aegypti mosquitoes, Rio de Janeiro, Brazil. Emerg Infect Dis. 2017 Aug;23(8):1411-1412.
https://wwwnc.cdc.gov/eid/article/23/8/16-2007_article
http://www.ncbi.nlm.nih.gov/pubmed/28628464?tool=bestpractice.com
Eighty-six countries, territories, and subnational areas have reported evidence of mosquito-borne Zika virus transmission.[26]World Health Organization. Zika virus classification tables. March 2018 [internet publication].
http://www.who.int/emergencies/zika-virus/classification-tables/en/
Transmission is ongoing in the Americas, the Western Pacific region, the Southeast Asia region, and Africa.
As of August 1, 2018, 5716 cases have been reported in US states (5430 cases in returning travelers, 231 cases acquired through presumed local mosquito-borne transmission in Florida and Texas, and 55 cases acquired through other routes), and 37,262 cases have been reported in US territories (most via local mosquito-borne transmission).[27]Centers for Disease Control and Prevention. Zika virus: case counts in the US. August 2018 [internet publication].
https://www.cdc.gov/zika/reporting/case-counts.html
As of July 17, 2018, the US Zika Pregnancy Registry and the Zika Active Pregnancy Surveillance System in Puerto Rico have reported 2474 pregnant women with any laboratory evidence of possible Zika virus infection in US states and the District of Columbia, and 4900 pregnant women in US territories.[28]Centers for Disease Control and Prevention. Pregnant women with any laboratory evidence of possible Zika virus infection in the United States and territories. July 2018 [internet publication].
http://www.cdc.gov/zika/geo/pregwomen-uscases.html
Among 478 confirmed cases in Miami-Dade County, Florida, 6.9% of cases occurred in children ages 1 to 17 years.[29]Griffin I, Zhang G, Fernandez D, et al. Epidemiology of pediatric Zika virus infections. Pediatrics. 2017 Dec;140(6). pii: e20172044.
http://www.ncbi.nlm.nih.gov/pubmed/29093135?tool=bestpractice.com
In the US, local transmission has previously been reported in Florida and Texas. Pregnant women and people living in or traveling to either of these areas should consult current Centers for Disease Control and Prevention (CDC) guidance. The CDC classifies geographic areas in the US and Hawaii as either red (active transmission areas) or yellow (cautionary areas), and this classification affects local guidance for pregnant women.[30]Centers for Disease Control and Prevention. Guidance for areas with local Zika virus transmission in the continental United States and Hawaii. May 2018 [internet publication].
https://www.cdc.gov/zika/geo/domestic-guidance.html
CDC: advice for people living in or traveling to South Florida
CDC: advice for people living in or traveling to Brownsville, Texas
CDC: guidance for areas with local Zika virus transmission in the continental United States and Hawaii
Cases in returning travelers have been reported in, but not limited to, locations including the US, UK, Europe, Australia, New Zealand, Israel, Japan, and China.[27]Centers for Disease Control and Prevention. Zika virus: case counts in the US. August 2018 [internet publication].
https://www.cdc.gov/zika/reporting/case-counts.html
[31]Gulland A. First case of Zika virus spread through sexual contact is detected in UK. BMJ. 2016 Dec 1;355:i6500.
http://www.bmj.com/content/355/bmj.i6500.long
http://www.ncbi.nlm.nih.gov/pubmed/27908879?tool=bestpractice.com
[32]Craig AT, Butler MT, Pastore R, et al. Acute flaccid paralysis incidence and Zika virus surveillance, Pacific Islands. Bull World Health Organ. 2017 Jan 1;95(1):69-75.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5180343/
http://www.ncbi.nlm.nih.gov/pubmed/28053366?tool=bestpractice.com
[33]Zammarchi L, Tappe D, Fortuna C, et al. Zika virus infection in a traveller returning to Europe from Brazil, March 2015. Euro Surveill. 2015 Jun 11;20(23). pii: 21153.
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=21153
http://www.ncbi.nlm.nih.gov/pubmed/26084316?tool=bestpractice.com
[34]Public Health England. Zika virus (ZIKV): clinical and travel guidance. August 2017 [internet publication].
https://www.gov.uk/government/collections/zika-virus-zikv-clinical-and-travel-guidance
[35]O’Dowd A. UK records four cases of Zika virus in past six weeks. BMJ. 2016 Feb 11;352:i875.
http://www.bmj.com/content/352/bmj.i875
http://www.ncbi.nlm.nih.gov/pubmed/26868672?tool=bestpractice.com
[36]Bachiller-Luque P, Domínguez-Gil González M, Álvarez-Manzanares J, et al. First case of imported Zika virus infection in Spain. Enferm Infecc Microbiol Clin. 2016 Apr;34(4):243-6.
http://www.ncbi.nlm.nih.gov/pubmed/26994814?tool=bestpractice.com
[37]Meltzer E, Lustig Y, Leshem E, et al. Zika virus disease in traveler returning from Vietnam to Israel. Emerg Infect Dis. 2016 Aug;22(8):1521-2.
http://wwwnc.cdc.gov/eid/article/22/8/16-0480_article
http://www.ncbi.nlm.nih.gov/pubmed/27331627?tool=bestpractice.com
[38]Taira M, Ogawa T, Nishijima H, et al. The first isolation of Zika virus from a Japanese patient who returned to Japan from Fiji in 2016. Jpn J Infect Dis. 2017 Mar 28 [Epub ahead of print].
https://www.jstage.jst.go.jp/article/yoken/advpub/0/advpub_JJID.2017.042/_article
http://www.ncbi.nlm.nih.gov/pubmed/28367888?tool=bestpractice.com
As of November 2017, 305 cases were reported in the UK, all of them associated with travel.[39]Public Health England. Zika virus: epidemiology and cases diagnosed in the UK. November 2017 [internet publication].
https://www.gov.uk/government/publications/zika-virus-epidemiology-and-cases-diagnosed-in-the-uk/zika-virus-epidemiology-and-cases-diagnosed-in-the-uk
Between June 2015 and January 2017, 21 countries in the European Union reported 2133 confirmed cases of infection (106 cases in pregnant women).[40]Spiteri G, Sudre B, Septfons A, et al. Surveillance of Zika virus infection in the EU/EEA, June 2015 to January 2017. Euro Surveill. 2017 Oct;22(41).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5710121/
http://www.ncbi.nlm.nih.gov/pubmed/29043960?tool=bestpractice.com
An association between Zika virus infection and fetal microcephaly, as well as other birth defects, was first reported in the current outbreak in October 2015.[41]Kleber de Oliveira W, Cortez-Escalante J, De Oliveira WT, et al. Increase in reported prevalence of microcephaly in infants born to women living in areas with confirmed Zika virus transmission during the first trimester of pregnancy - Brazil, 2015. MMWR Morb Mortal Wkly Rep. 2016 Mar 11;65(9):242-7.
http://www.cdc.gov/mmwr/volumes/65/wr/mm6509e2.htm
http://www.ncbi.nlm.nih.gov/pubmed/26963593?tool=bestpractice.com
The prevalence of birth defects potentially related to Zika virus infection was reported to be 3 per 1000 live births in a birth cohort of nearly 1 million births in 2016.[42]Delaney A, Mai C, Smoots A, et al. Population-based surveillance of birth defects potentially related to Zika virus infection - 15 states and U.S. territories, 2016. MMWR Morb Mortal Wkly Rep. 2018 Jan 26;67(3):91-96.
https://www.cdc.gov/mmwr/volumes/67/wr/mm6703a2.htm
http://www.ncbi.nlm.nih.gov/pubmed/29370151?tool=bestpractice.com
Data from the US Zika Pregnancy Registry found that 10% of pregnancies with laboratory-confirmed infection resulted in fetuses/infants with birth defects. This figure increases to 15% when restricting the analysis to the first trimester.[43]Reynolds MR, Jones AM, Petersen EE, et al; US Zika Pregnancy Registry Collaboration. Vital signs: update on Zika virus-associated birth defects and evaluation of all US infants with congenital Zika virus exposure - US Zika Pregnancy Registry, 2016. MMWR Morb Mortal Wkly Rep. 2017 Apr 7;66(13):366-373.
https://www.cdc.gov/mmwr/volumes/66/wr/mm6613e1.htm?s_cid=mm6613e1_w
http://www.ncbi.nlm.nih.gov/pubmed/28384133?tool=bestpractice.com
This report covered cases reported in US states only. A more robust study of completed pregnancies in women with laboratory evidence of Zika virus infection in US territories found approximately 1 in 20 (5%) fetuses or infants had a possible Zika-associated birth defect. When the analysis was restricted to confirmed infection in the first trimester, the rate increased to 1 in 12 (8%).[44]Shapiro-Mendoza CK, Rice ME, Galang RR, et al; Zika Pregnancy and Infant Registries Working Group. Pregnancy outcomes after maternal Zika virus infection during pregnancy - US territories, January 1, 2016-April 25, 2017. MMWR Morb Mortal Wkly Rep. 2017 Jun 16;66(23):615-621.
https://www.cdc.gov/mmwr/volumes/66/wr/mm6623e1.htm
http://www.ncbi.nlm.nih.gov/pubmed/28617773?tool=bestpractice.com
An association between Zika virus infection and GBS was first reported in the current outbreak in July 2015. Current evidence estimates the incidence of GBS to be 24 cases per 100,000 persons infected with Zika.[45]Uncini A, Shahrizaila N, Kuwabara S. Zika virus infection and Guillain-Barré syndrome: a review focused on clinical and electrophysiological subtypes. J Neurol Neurosurg Psychiatry. 2017 Mar;88(3):266-271.
http://www.ncbi.nlm.nih.gov/pubmed/27799296?tool=bestpractice.com
GBS has not been reported in children.[46]Goodman AB, Dziuban EJ, Powell K, et al. Characteristics of children aged <18 Years with Zika virus disease acquired postnatally - US states, January 2015-July 2016. MMWR Morb Mortal Wkly Rep. 2016 Oct 7;65(39):1082-1085.
https://www.cdc.gov/mmwr/volumes/65/wr/mm6539e2.htm?s_cid=mm6539e2_w
http://www.ncbi.nlm.nih.gov/pubmed/27711041?tool=bestpractice.com
CDC: Zika virus case counts in the US
WHO: Zika virus classification tables