Zika virus: epidemiology and cases diagnosed in the UK

Updated 25 May 2017

1. History

Zika virus was first isolated from a monkey in the Zika forest in Uganda in 1947. The virus circulates in Africa and Asia in humans, animals and mosquitoes but prior to 2015 few outbreaks were 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.

2. Current outbreaks

Since the report of the first locally-acquired confirmed case of Zika infection in Brazil in May 2015, many countries, territories and areas in South and Central America, the Caribbean, Oceania (Melanesia, Micronesia and Polynesia only) and South East Asia have reported Zika virus transmission.

As surveillance for Zika virus infection improves, further cases are expected to be reported in these regions and previously unaffected countries, territories and areas.

Further information on countries, territories and areas reporting Zika virus transmission to inform travel advice can be found on the country-specific risk page.

ECDC provides information on countries, territories and areas with active transmission in the last 9 months which can be used to aid diagnosis in returning travellers, especially pregnant women with travel history during pregnancy.

3. Zika cases diagnosed in the UK

The vector which transmits Zika virus is not found in the UK, and almost all cases are associated with travel to countries, territories or areas with active Zika virus transmission.

As of 24 May 2017, 299 travel-associated cases have been diagnosed since 2015. Of these, 201 are confirmed cases including:

  • 151 cases with virus detected [PCR positive]
  • 50 cases with antibody evidence indicating recent infection [seroconversion]

and 98 cases with antibody evidence highly indicative of recent infection (Zika-specific IgM) [probable cases].

Of the total 299 travel-associated cases reported, eight have been diagnosed in pregnant women.

In addition, one case of likely sexual transmission of Zika virus infection has been reported in the UK.

3.1 Region of travel for Zika cases diagnosed in UK travellers since 2015

Region of travel Total
Caribbean 216
Central America 34
South America 34
South-Eastern Asia 6
North America* 2
Oceania 1
More than one region 5
Not stated 1
Grand total 299

*The cases acquired in North America had travelled to the high risk area of Miami-Dade County in Florida

The majority of Zika cases in the UK have travelled to the Caribbean and South and Central America.

More than two-thirds of cases have travelled to the Caribbean; the six most frequently reported countries of travel are Antigua, Barbados, Grenada, Jamaica, St Lucia and Trinidad and Tobago – all countries popular with UK travellers including those visiting friends and relatives.

Of those that travelled to South and Central America, most have reported travel to Brazil, Colombia, Mexico, Nicaragua and Venezuela.

4. WHO Emergency Committee declaration

The WHO International Health Regulations (IHR) Emergency Committee (EC) has met on 5 occasions regarding Zika virus. Zika virus, and its association with microcephaly and other neurological disorders, was declared a Public Health Emergency of International Concern (PHEIC) as defined under the IHR (2005) on 1 February 2016.

At the latest meeting on 18 November 2016, the EC felt that Zika virus and its associated consequences remains a significant and enduring public health challenge requiring intense action but no longer represented a PHEIC under IHR (2005). Under this advice, the WHO Director General has declared the end to the PHEIC.

The WHO has reissued the Temporary Recommendations from the previous EC meetings which include:

  • improved surveillance and control of Zika in at risk countries
  • measures for travellers and pregnant women

However, these recommendations will be incorporated into a longer term response mechanism already outlined in the WHO Zika Strategic Response Plan.