Zika Virus Infection
First published: 29 January 2016
Previous update: 25 November 2016
This update: 27 April 2017
The WHO announced on 10 March 2017 an updated classification of countries at risk of Zika virus to reflect the evolving epidemiology of Zika Virus. This included countries where the principal vector Aedes aegypti is present, but are not yet known to have Zika virus circulating.
The Travel and International Health Team of Health Protection Scotland, in conjunction with Public Health England, are currently assessing the new classification scheme in order to amend the national guidance for those travelling to Zika affected countries.
Further updates will be posted when this assessment process is complete
Discovered opportunistically in monkeys in Uganda Zika virus (ZIKV) is a flavivirus which causes relatively mild disease. The virus is transmitted by mosquitoes of the genus Aedes. In 2007 an outbreak in the Yap Island in the Federated States of Micronesia was the first time ZIKV transmission had occurred outside Africa and Asia. In 2013 a further outbreak was reported in French Polynesia which continued into 2014 and in which the first cases of possible perinatal transmission and Gullain-Barré syndrome (GBS) were reported. Further outbreaks in Pacific Islands were reported in 2014 and 2015.
In 2015 the first outbreaks were reported in South and Central America. In May 2015 ZIKV was suspected and then confirmed in the North East of Brazil. Other parts of Brazil soon reported outbreaks as did other countries in the Region. Further cases were also reported from the Caribbean Islands.
Countries/territories/areas are assigned into categories of risk of ZIKV transmission as determined by data provided by ECDC. The outbreak of ZIKV is evolving; the risk of transmission in countries/territories/areas changes as the outbreak progresses and these categories are regularly updated. For the purposes of pre-travel guidance, the risk has been defined as below:
ZIKV Outbreak in Brazil and Observations of Microcephaly
Since early 2015 ZIKV has been reported in twenty Brazilian states with estimates of cases ranging from 440,000 to 1.3 million by late 2015. Of greater concern was the observed increase (20 fold) reported in October 2015 in developmental defects including microcephaly among babies in Brazil; observed as part of routine surveillance by Brazil’s Ministry of Health. These microcephaly cases were reported in the main in the North east of the country. There is now strong evidence of causation between ZIKV and neurodevelopmental defects.
The occurrence of neurodevelopmental defects in Brazil, with the possible link to ZIKV, was declared a Public Health Emergency of International Concern (PHEIC) by WHO on 1 February. The PHEIC ended on 18th November 2016 and is replaced by a longer term response detailed in the Zika Strategic Response Plan.
- The risk to Scotland is considered very low due to the absence of the Aedes mosquito and the low risk associated with sexual transmission associated with imported cases.
- For travellers to affected countries there is a low risk of infection which may result in mild symptoms in the majority of cases.
- For pregnant travellers or for women who may become pregnant during or soon after travel the risk is considered higher due to the association of ZIKV infection and Congenital Zika Syndrome.
- There is a low risk of sexual transmission of ZIKV.
HPS Recommendations for travellers to countries where ZIKV is circulating
Advice for the travelling public can be found on our fitfortravel website for countries/territories/areas with High, Moderate, Low and Very Low risk of ZIKV.
- There is no medicine or vaccine available that prevents ZIKV infection.
- The most effective/important way to avoid infection is to prevent mosquito bites by using insect repellents and wearing appropriate clothing.
The following is advice for All Travellers to areas with High or Moderate risk of ZIKV transmission:
- Seek travel advice from a health care provider at least 6-8 weeks in advance of travel, but particularly important if pregnant or planning pregnancy.
- Strongly advised not to travel without adequate insurance – pregnant women should check with their travel insurance company that they are covered under the policy.
- Mosquito bite avoidance is strongly recommended
- The mosquitoes which transmit ZIKV are particularly persistent and aggressive biters. HPS recommends DEET(diethyltoluamide) based insect repellents at a concentration of 50%, which should be applied regularly. DEET up to 50% is appropriate for use in pregnancy. If DEET is unsuitable then another, proven alternative should be used, for example Icaridin or PMD (Lemon Eucalyptus). Active ingredients are listed on the product label and manufacturers instructions should be followed.
- Wearing loose, cover-up clothing is recommended. Clothing can be impregnated with permethrin.
Insecticide-impregnated bed nets and air conditioning should be used in bedrooms. Reduction of mosquito breeding sites around hotel rooms/homes is advised for longer-term stays.
- Travellers from countries affected by ZIKV cannot donate blood for 4 weeks after return if they have had no symptoms, or 6 months if they have had symptoms of ZIKV infection.
The following is advice for Women who are Pregnant travelling to areas with High risk of ZIKV transmission:
- Advised to postpone non-essential travel to countries with active ZIKV transmission until the link between ZIKV and adverse pregnancy outcomes has been fully clarified.
The following is advice for Women who are Pregnant travelling to areas with Moderate risk of ZIKV transmission:
- Consider postponing non-essential travel to countries with active ZIKV transmission until the link between ZIKV and adverse pregnancy outcomes has been fully clarified.
If travel is essential, they should be helped to understand the risks in order to make a fully informed decision.
- During travel, strict bite avoidance is essential.
- Should abstain, or use condoms, to reduce the risk of sexual transmission of ZIKV during travel and throughout the pregnancy.
- On return, early obstetric review is recommended even if well.
- Medical attention must be sought quickly for any feverish illness experienced whilst travelling or on return.
The following is advice for non-pregnant women travelling to areas with High or Moderate risk of ZIKV tranmission:
- Non-pregnant women should abstain, or use contraception and condoms during travel and for 8 weeks afterwards to avoid the risk of ZIKV in an unplanned pregnancy and sexual transmission of ZIKV.
The following is advice for Men travelling to areas with High or Moderate risk of ZIKV transmission :
- Men irrespective of symptoms, should abstain, or use condoms, during travel and for 6 months after travel to reduce the risk of sexual transmission of ZIKV, particularly during conception or pregnancy.
Advice for those travelling to areas with Low risk of ZIKV transmission:
- The risk of ZIKV transmission during travel is low, but ZIKV infection in pregnancy may lead to adverse pregnancy outcomes. Pregnant women and women planning pregnancy should discuss the risk of ZIKV with their travel health provider before deciding whether to continue with travel plans.
- Travellers who develop illness during travel should seek medical attention at their destination. Those who are diagnosed with ZIKV should:
- Pregnant woman - use condoms during travel and for 8 weeks afterwards to reduce the risk of sexual transmission and seek early obstetric review.
- Non pregnant women should use contraception and condoms during travel and for 8 weeks afterwards to avoid the risk of ZIKV in an unplanned pregnancy and sexual transmission of ZIKV.
- Men should use condoms during travel and for 6 months after travel to avoid the risk of sexual transmission of ZIKV, particularly during conception or pregnancy.
Diagnosis and reporting
- Clinicians are advised to consider the possibility of ZIKV in patients presenting with a febrile illness on return from regions where the infection is present, or whose female sexual partner has returned in the last 8 weeksor whose male sexual partner has returned in the last 6 months from regions where the infection is present. This is particularly important for women of childbearing age who are, or may be pregnant.
- Any requests for testing have to be directed to Public Health England's (PHE) Rare and Imported Pathogens Laboratory (RIPL).
- Virology testing should only be undertaken in those with current symptoms. Clinicians ordering virology tests for patients with a relevant travel history should be explicit in requesting ZIKV PCR and should indicate the country and region of travel on the request form and whether pregnant, partner pregnant and gestation (submit samples using the RIPL referral form P1).Clinicians should send samples to the local laboratory who will carry out appropriate procedures and forward samples.
- Serological tests to confirm recent/previous infection in those with a history of symptoms is available from RIPL see https://www.gov.uk/guidance/zika-virus-sample-testing-advice. Serum (+/- urine) samples should be submitted to the local virus laboratory accompanied by a completed RIPL form (see above) for those with: previous compatible symptoms occurring during, or within 2 weeks of travel to regions where the infection is present, or in those with previous compatible symptoms whose female sexual partner has returned in the last 8 weeks or whose male sexual partner has returned in the last 6 months from regions where the infection is present.
- If typical ZIKV infection-like symptoms develop between 8 weeks and 6 months after an individual’s male sexual partner has left a ZIKV affected country the case should be discussed first with RIPL before samples are sent for testing.
- Clinicians should liaise with obstetric colleagues to raise awareness and ensure appropriate investigations and counselling are in place for pregnant female patients with a relevant travel history. Negative serology taken 4 weeks after the last possible exposure to ZIKV, excludes infection. This testing is available to previously symptomatic pregnant women; negative antibody results indicate they do not require extra fetal ultrasound follow-up, unless there are additional concerns. This is arranged through obstetric services
- In Scotland, clinicians who require help with risk assessment and diagnosis of ZIKV in an individual presenting to them should seek advice from their local infectious disease consultant
- In Scotland, reporting of ZIKV is through HPS. For the rest of the UK this is directly through Public Health England.
Public Health Implications
- The main risk is in Latin America, in particular Brazil. Until further evidence is available, a precautionary approach to the risk posed by ZIKV, in particular during pregnancy, is being adopted by public health authorities worldwide.
- The evidence for the involvement of ZIKV infection in microcephaly is increasing. The number of cases of microcephaly in Brazil is under review, as is the nature of association between ZIKV and developmental abnormalities.
- The link with GBS is also under investigation. GBS has been reported from some countries currently experiencing an outbreak of ZIKV; GBS appears to be a rare sequela to ZIKV and investigations are ongoing to establish a causal link.
- ZIKV has been detected in semen some months after clinical symptoms of ZIKV and for some weeks in the female genital tract; a small, but growing number of sexually transmitted cases of ZIKV infection have been reported worldwide.
- Evidence for perinatal and transplacental transmission has been reported.
- In terms of vector control in flights from affected countries the International Health Regulations Emergency Committee on Zika virus has advised that standard WHO recommendations on disinsection of aircraft and airports should be implemented in order to control Aedes sp mosquitoes. Airlines with flights into Scotland from affected countries are following these guidelines.
Further Advice for clinicians
Updates on Countries
Managing Pregnant women