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Zika Virus Infection

First published:   29 January 2016
Previous update:  27 April 2017
This update:         8 August 2017

Update Summary:
The WHO announced on 10 March 2017 an updated classification of countries at risk of Zika virus to reflect the evolving epidemiology of the virus. This included countries where the principal vector Aedes aegypti is present, but are not yet known to have Zika virus circulating.

Health Protection Scotland, in conjunction with Public Health England, have assessed this updated classification. The High, Moderate and Low risk categories for Zika virus transmission produced by PHE have been adapted to reflect this update.

Background

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 on 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 /16 ZIKV spread throughout South and Central America, the Caribbean and parts of North America.

ZIKV Outbreak in Brazil and Observations of Microcephaly

The spread of ZIKV into South America coincided with an observed increase in microcephaly and developmental defects in neonates and led to a Public Health Emergency of International Concern (PHEIC) being declared by WHO. This ran from February to November 2016 and is replaced by a longer term Zika Strategic Response Plan.

Since 2016, ZIKV infection in pregnancy has been established as the cause of Congenital Zika Syndrome, that may have severe and fatal consequences for the fetus. Sexual transmission of ZIKV, a rare event has been documented. In addition ZIKV infection may result in Guillain-Barré syndrome.

Risk assessment

  • The risk to Scotland is considered very low due to the absence of the Aedes mosquito and the low risk of 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

The risk of ZIKV transmission (High, Moderate and Low)in affected countries can be accessed here.

Advice for the travelling public can be found on our fitfortravel website.

Prevention

  • There is no medicine or vaccine currently 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.

Women who are Pregnant travelling to areas with High risk of ZIKV transmission are advised to postpone non-essential travel.

Women who are Pregnant travelling to areas with Moderate risk of ZIKV transmission should be advised to consider postponing non-essential travel.

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.
  • They 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.

Those planning pregnancy, or where there is a risk of pregnancy and travelling to areas with High or Moderate risk of ZIKV tranmission, avoid the risk of ZIKV in pregnancy and sexual transmission of ZIKV by the use of contraception and condoms during travel and for:

  • 8 weeks afterwards if female
  • 6 months afterwards if male

Women who are pregnant and those planning pregnancy travelling to areas with Low risk of ZIKV transmission should be advised that ZIKV infection in pregnancy may lead to adverse pregnancy outcomes. They 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.
    • All other individuals, follow contraception advice and ways of preventing onward sexual transmission as detailed above.

Diagnosis and reporting

  • Clinicians are advised to consider the possibility of ZIKV in patients presenting with a febrile illness on return from countries with a high or moderate risk of ZIKV or whose sexual partner has returned from these countries (in the last 8 weeks if female partner or 6 months if male partner) 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).
  • Testing should only be undertaken in those with current or a history of symptoms. Clinicians ordering tests for patients with a relevant travel history should be explicit in requesting ZIKV testing 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 see https://www.gov.uk/guidance/zika-virus-sample-testing-advice.
    • 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. 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

  • 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.
  • 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.
  • 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 should be implemented in order to control Aedes sp mosquitoes.

Further Advice for clinicians

Updates on Countries

Managing Pregnant women

Other