Updated: Cuba and Dominica added to country listing; update to UK case numbers.
Zika is a mosquito-borne infection caused by Zika virus, a member of the genus flavivirus and family Flaviviridae. It was first isolated from a monkey in the Zika forest in Uganda in 1947.
travel advice: see NaTHNaC current advice
assessment of pregnant women following travel: see algorithm
advice for those working in primary care: see primary care guidance
deferral of blood donation: see NHS Blood and Transplant
information for the public about Zika virus: see NHS Choices
media enquiries: contact press office
Areas with active Zika virus transmission
The UK defines areas with active Zika virus transmission as countries, overseas territories or specific areas within countries (where this is known) in which there is current active Zika virus transmission as classified by the European Centre for Disease Control (ECDC).
For a country or overseas territory to be classified as having current active Zika virus transmission there must be: confirmed autochthonous (locally acquired) cases, acquired by vector borne transmission only, that have been reported by Health authorities within the last 2 months (* in table below).
Areas with active transmission in the last 9 months are also provided to aid diagnosis for returning travellers, especially pregnant women with travel history during pregnancy. As of 16 March 2016, areas with active Zika virus transmission are:
Caribbean
Central America
South America
Pacific
Other
Aruba*
Costa Rica*
Bolivia*
American Samoa*
Cape Verde*
Barbados*
El Salvador*
Brazil*
Fiji*
Thailand*
Bonaire*
Guatemala*
Colombia*
Marshall Islands*
Philippines*
Cuba*
Honduras*
Ecuador*
New Caledonia*
Curaçao*
Mexico*
French Guiana*
Samoa*
Dominica*
Nicaragua*
Guyana
Solomon Islands
Dominican Republic*
Panama*
Paraguay*
Tonga*
Guadeloupe*
Suriname*
Vanuatu
Haiti*
Venezuela*
Jamaica*
Martinique*
Puerto Rico*
Saint Martin*
Sint Maarten*
St Vincent and the Grenadines*
Trinidad and Tobago*
US Virgin Islands*
* Areas with active transmission in the last two months
Prior to 2015, Zika virus outbreaks occurred in areas of Africa, Southeast Asia, and the Pacific Islands.
As surveillance for Zika improves, further cases of Zika are expected to be reported in these regions and previously unaffected countries, particularly in south and central America and the Caribbean, where the Aedes mosquito vector is present.
Epidemiology
Zika virus was first discovered in Africa in the 1940s. The virus circulates in Africa and Asia in humans, animals and mosquitoes but prior to 2015 few outbreaks have been documented.
The first Zika outbreak reported outside Africa and Asia occurred on Yap Island in the Federated States of Micronesia in 2007. It was caused by the Asian strain of the virus. The same strain caused a subsequent outbreak in French Polynesia in 2013 and has since caused large outbreaks in other parts of the Pacific region including the first cases in the Americas on Easter Island (a Chilean island in the south east Pacific) in 2014.
In May 2015, the first locally-acquired confirmed case of Zika infection was reported in Brazil.
Zika cases diagnosed in the UK
ZIKV does not occur naturally in the UK. However, as of 16 March 2016, a total of 12 cases have been diagnosed in UK travellers.
Country of travel
2014
2015
2016
Total
Barbados
-
-
2
2
Brazil
-
-
1
1
Colombia
-
1
2
3
Cook Islands*
1
-
-
1
Curaçao/Venezuela
-
-
1
1
Guyana/Suriname
-
1
-
1
Jamaica
1
1
Mexico/Venezuela
-
-
1
1
Venezuela
-
-
1
1
Total
1
2
9
12
* Not associated with current outbreak. Although cases have previously been reported in the Cook Islands, active transmission of Zika virus is not known to be ongoing.
Symptoms
The majority of people infected with Zika virus have no symptoms. For those with symptoms, Zika virus tends to cause a mild, short-lived (2 to 7 days) febrile disease. Signs and symptoms suggestive of Zika virus infection may include a combination of the following:
fever
rash
arthralgia/arthritis
conjunctivitis
myalgia
headache
retro-orbital pain
pruritus
The symptoms of Zika are similar to dengue (caused by a related flavivirus) or chikungunya (an alphavirus), which are often co-circulating in areas where Zika virus is present. Laboratory testing is essential for the correct diagnosis.
Serious complications and deaths from Zika are not common. However, recent increases in congenital anomalies (particularly microcephaly), Guillain-Barré syndrome, and other neurological and autoimmune syndromes are being reported in areas where Zika outbreaks have occurred. The association of these illnesses with Zika virus is temporal and causality has yet to be proven, however evidence is accumulating. Further information about these findings is available from WHO.
Following an International Health Regulations (IHR) Emergency Committee (EC) meeting on 1 February 2016, it was declared that the recent cluster of microcephaly cases and other neurological disorders reported in Brazil, following a similar cluster in French Polynesia in 2014, constitutes a Public Health Emergency of International Concern (PHEIC). In the absence of another explanation for these clusters, it was advised by the Emergency Committee (EC) that these clusters were possibly associated with the recent outbreaks of Zika virus. The World Health Organization (WHO) has issued temporary recommendations which include: improved surveillance and control of Zika in at risk countries, and measures for travellers and pregnant women.
The WHO has launched a global Zika Emergency Response Plan to guide the international response to the spread of Zika virus infection and the neonatal malformations and neurological conditions associated with it.
Transmission
Zika virus is transmitted by the bite of an infected female Aedes mosquito, most commonly Aedes aegypti. Other species of Aedes mosquitoes may also have the potential to transmit this virus. The Aedes aegypti mosquito is not present in the UK and is unlikely to establish in the near future as the UK temperature is not consistently high enough for it to breed.
After an infected mosquito bites a human, the first symptoms of Zika can develop in 3 to 12 days but it can be shorter or longer in some people.
While almost all cases of Zika are acquired via mosquito bites, a small number of cases have occurred through sexual transmission, and there is increasing evidence of transmission from mother to fetus via the placenta.
Transmission of Zika via blood transfusion has been suspected in a small number of cases, and a study during the outbreak in French Polynesia detected Zika virus in 3% of blood donors who were asymptomatic at the time of donation. Measures to safeguard the UK blood supply are being implemented from 4 February 2016.
If a person acquires Zika abroad and becomes ill on their return to the UK, any public health risk to the wider population is negligible, as the mosquito that transmits the virus is not found in the UK.
HAIRS assessment of the risk that Zika virus presents to the UK population
Advice for all travellers
There is currently no vaccine or drug to prevent Zika virus infection.
Aedes mosquitoes, most commonly Aedes aegypti, transmit Zika as well as diseases such as chikungunya, dengue, and yellow fever. Aedes mosquitoes predominantly bite during the day, but especially during mid-morning and late afternoon to dusk (as opposed to mosquitoes that transmit malaria, which bite at night between dusk and dawn).
Travellers to regions where these diseases occur should ideally seek travel health advice from their GP, practice nurse or a travel clinic at least 4-6 weeks before they travel. Even if time is short it is still not too late to get travel advice.
UK nationals who live in areas with active Zika transmission and have concerns, should seek advice from their local healthcare provider who will be able to advise on their individual circumstances.
Up to date travel advice for areas reporting active Zika transmission is available from the National Travel Health Network and Centre (NaTHNaC).
Preventing infection by mosquito bites
All travellers should take insect bite avoidance measures during daytime and night time hours to reduce the risk of infection with Zika and other mosquito borne diseases.
A good repellent containing N, N-diethylmetatoluamide (DEET) should be used on exposed skin, together with light cover-up clothing. If sunscreen is needed, repellent should be applied after sunscreen. Sunscreen should be 30 SPF or above to compensate for DEET- induced reduction in SPF.
Leaflet: Mosquito bite avoidance for travellers
Preventing infection by sexual transmission
A small number of cases of sexual transmission of Zika virus have been reported. In a limited number of cases, the virus has been shown to be present in semen, although it is not yet known how long this can persist. The risk of sexual transmission of Zika virus is considered to be low, but the number of reports is increasing.
Zika is usually an asymptomatic or mild illness. Couples who wish to reduce the risk of transmission may consider using condoms if the man had clinical illness compatible with Zika virus infection. Condom use should commence at the onset of the illness and continue for 6 months.
This is a precaution and may be revised as more information becomes available. Individuals with further concerns regarding potential sexual transmission of Zika virus and options for contraception should contact their GP for advice.
There is increasing evidence to suggest that Zika virus infection may present an increased risk for certain groups of the population, particularly pregnant women. Specific advice has been developed for these groups (see below).
Pregnant women and their male partners who are planning to travel
Pregnant women should discuss their travel plans with their healthcare provider to assess their risk of infection with Zika virus and, where travel is unavoidable, receive advice on mosquito bite avoidance measures. Information on factors to consider when assessing the risk of infection with Zika is available from NaTHNaC.
it is recommended that pregnant women planning to travel should postpone non-essential travel to areas with active Zika transmission until after pregnancy
in the event that travel to an area with active Zika virus transmission cannot be postponed, the pregnant traveller must be informed by the healthcare provider of the risks which Zika may present
the use of scrupulous mosquito bite avoidance measures both during daytime and night time hours (but especially during mid-morning and late afternoon to dusk, when the mosquito is most active) should be emphasised, and an information leaflet provided
if a female partner is pregnant, condom use is advised for a male traveller to reduce the risk of transmission during travel and for the duration of the pregnancy
Pregnant women who have travelled
Pregnant women who have recently travelled in an area reporting active Zika virus transmission in the last 9 months should seek advice from their GP or midwife on their return to the UK, even if they have not been unwell.
Further information about when to perform fetal ultrasound scanning, and, if necessary, referral to the local fetal medicine service, is available.
For pregnant women who are experiencing current symptoms suggestive of Zika virus infection, see Diagnosis for further information.
Women planning pregnancy and their male partners
Women who are planning to become pregnant should discuss their travel plans with their healthcare provider to assess their risk of infection with Zika virus and, where travel is unavoidable, receive advice on mosquito bite avoidance measures. Information on factors to consider when assessing the risk of infection with Zika is available from NaTHNaC.
women should be advised on the potential risks of Zika virus infection in pregnancy. It is recommended that women should avoid becoming pregnant while travelling in an area with active Zika virus transmission, and for 28 days after their return. This allows for a maximum 2-week incubation period (the time between exposure to an infection and the appearance of the first symptoms) and a possible 2-week viraemia (presence of virus in the bloodstream). Following this, attempts to conceive can resume
in addition, the use of scrupulous mosquito bite avoidance measures both during daytime and night time hours (but especially during mid-morning and late afternoon to dusk, when the mosquito is most active) should be emphasised, and an information leaflet provided
if a woman planning pregnancy develops symptoms compatible with Zika virus infection on her return to the UK, please see Diagnosis. It is recommended she avoids becoming pregnant for a further 28 days following recovery
If a female partner is at risk of getting pregnant, or is planning pregnancy, effective contraception is advised to prevent pregnancy AND condom use is advised for a male traveller to reduce the risk of transmission during travel and:
for 28 days after his return from an active Zika transmission area if he has not had any symptoms compatible with Zika virus infection
for 6 months following the start of symptoms if a clinical illness compatible with Zika virus infection or laboratory confirmed Zika virus infection was reported
This is a precaution and may be revised as more information becomes available.
Following this, attempts to conceive can resume.
Immunocompromised individuals
Guidance providing practical advice for clinicians caring for immunocompromised persons wishing to travel to Zika affected areas is available.
Zika virus, travel and immunocompromised patients
Guidance for primary care
Guidance for primary care and clinicians has been jointly developed by PHE, Royal College of General Practitioners and the British Medical Association.
Zika virus infection: guidance for primary care
Zika virus infection is not a notifiable disease in England.
Zika and pregnancy
Interim algorithm for assessing pregnant women with a history of travel during pregnancy to areas with active Zika virus transmission.
Interim advice for health professionals
Zika virus briefing for midwives.
Women should be advised to avoid becoming pregnant while travelling in an area with active Zika virus transmission, and for 28 days after their return. (This allows for a maximum 2-week incubation period (the time between exposure to an infection and the appearance of the first symptoms) and a possible 2-week viraemia (presence of virus in the bloodstream).
Zika and Guillain-Barré syndrome
Guillain-Barré syndrome is a rare neurological condition which can occur following Zika virus infection.
Zika virus and Guillain-Barré syndrome
Zika and immunocompromised patients
Guidance providing practical advice for clinicians caring for immunocompromised persons wishing to travel to areas with active Zika transmission.
Zika virus, travel and immunocompromised patients
Diagnosis
Consider Zika virus infection among the differential diagnoses of patients with fever, or other symptoms suggestive of Zika virus infection, returning from countries with active Zika virus transmission (as listed above).
Clinicians should also consider in the differential diagnosis other travel-associated infections, including dengue and chikungunya virus infections, malaria, common infections not associated with travel, and non-infectious diseases.
Diagnostic testing is only indicated for a patient who
has travelled to or arrived from an area with active Zika virus transmission and
within 2 weeks of return to the UK, has two or more symptoms suggestive of acute Zika virus infection at the time of assessment
Symptoms suggestive of acute Zika virus infection include: fever; rash; arthralgia/arthritis; conjunctivitis; myalgia; headache; retro-orbital pain; pruritus.
Testing can also be considered for pregnant women with acute onset of symptoms within 2 weeks of travel to an area with active Zika virus transmission if the symptoms are not explained by other common infectious causes (such as upper respiratory tract or urinary tract infections).
It is recommended that the following samples are obtained when testing is indicated:
non-pregnant patients: clotted ‘red top’ (plain) or ‘yellow top’ (serum separator) blood, and EDTA ‘purple top’ blood
pregnant patients: clotted ‘red top’ (plain) or ‘yellow top’ (serum separator) blood, EDTA ‘purple top’ blood, and a small volume of urine without preservative
For suspected cases of Zika virus infection, samples need to be sent to PHE’s Rare and Imported Pathogens Laboratory (RIPL); this should be done by liaising with the local diagnostic laboratory. In addition to completing any local laboratory request form, a RIPL request form also needs to be completed by the clinician assessing the patient.
RIPL provides medical and laboratory specialist services to the NHS and other healthcare providers for advice and diagnosis of a wide range of unusual bacterial and viral infections, including Zika virus infection.
This service is not available to the public.
Treatment
There is no specific antiviral treatment for Zika. Supportive nursing care and relief of symptoms are the standard treatment.