07 Dec 2015

Zika virus in the Americas: update and advice for pregnant women

Further information on the international spread of Zika virus (ZIKV) through the Americas

The first case of locally acquired Zika virus (ZIKV) in the Americas was reported from Easter Island (a Chilean island in the south east Pacific) during 2014; there were no further cases reported after June 2014 [1]. Brazil confirmed the first locally acquired cases of ZIKV in May, 2015. The disease has now spread to a number of countries in the Americas, and it is likely that other countries in the area will be affected in the future. View a map (updated weekly) showing countries and territories in the Americas with confirmed locally acquired cases of ZIKV.

ZIKV is a dengue-like virus that is transmitted by Aedes mosquitoes. The infection often occurs without symptoms but can also cause an illness similar to dengue. The condition is usually mild and short-lived; severe disease is uncommon [2]. However, as of 28 November 15, the Ministry of Health Brazil has reported three deaths associated with the ongoing ZIKV outbreak; an increase in congenital anomalies including microcephaly (an abnormally small head linked to incomplete brain development), Guillain-Barré syndrome, and other neurological and autoimmune syndromes has been reported and is under investigation [1, 3].

ZIKV was first isolated in Uganda in 1947 and up until 2007 had only been known to cause sporadic human infections in Africa and Asia. In 2007 the first outbreak of ZIKV occurring outside these regions was reported in the Federated States of Micronesia with a further connected outbreak occurring in French Polynesia in 2013. This outbreak subsequently spread to a number of other Pacific Island states including: Cook Islands, Easter Island (Chile) and New Caledonia [4].

The detection of circulating ZIKV in the Americas demonstrates the potential for the virus to spread to countries and continents where the Aedes mosquito vector is found.  The World Health Organization (WHO) has issued an alert recommending that member states, vulnerable to the introduction of ZIKV, establish and maintain appropriate measures for surveillance, control and clinical management of ZIKV infection [5].

Advice for travellers

Aedes mosquitoes transmit ZIKV, as well as diseases such as chikungunya, dengue and yellow fever. Aedes mosquitoes bite in the day, particularly around dawn and dusk. You should take insect bite avoidance measures to reduce the risk of infection with ZIKV and other mosquito borne diseases.

If you are pregnant, or planning to become pregnant and live in, or will be travelling to areas affected by ZIKV outbreaks, you should discuss your travel plans with your health care provider to assess your risk and receive advice on mosquito bite avoidance measures.

There is currently no vaccine available to prevent ZIKV.

Advice for health professionals

Health professionals can check for the latest disease outbreaks on our Outbreak Surveillance database. Outbreaks will also be shown in the outbreak section of our Country Information pages.

Health professionals should consider ZIKV among the differential diagnoses of patients with fever returning from the Americas. If a case of ZIKV is suspected, appropriate samples for testing (together with a full travel and clinical history with relevant dates) should be sent as early as possible to the Public Health England, Rare and Imported Pathogens Laboratory.

The Imported Fever Service: Public Health England is available to local infectious disease physicians or microbiologists should specialist advice be needed on 0844 7788990.

Health professionals should also be vigilant for any increase of neurological and autoimmune syndromes (in adults and children), or congenital malformations in new born infants (where the cause is not otherwise evident) in patients with a history of travel to areas where ZIKV transmission is known to occur [1].


  1. Pan American Health Organization (PAHO). Epidemiological Alert. Neurological syndrome, congenital malformations, and Zika virus infection. Implications for public health in the Americas. 1 December 2015 [Accessed 15 January 2016]
  2. US Centers for Disease Control and Prevention. Zika virus June 2015 [Accessed 15 January 2016].
  3. European Centres for Disease Prevention and Control. Rapid Risk Assessment: Microcephaly in Brazil potentially linked to the Zika virus epidemic. 25 November 2015 [Accessed 15 January 2016].
  4. Musso D, Nilles EJ and Cao-Lormeau VM. Rapid spread of emerging Zika virus in the Pacific area. Clin Microbiol Infect. 2014;20 (10):O595-596.
  5. World Health Organization. Weekly Epidemiological Report. Zika virus outbreaks in the Americas 6 November 2015; 45, 90: 609-16

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