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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 and South East Asia have reported Zika virus transmission.
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 or areas with active Zika virus transmission.
As of 26 July 2017, 14 travel-associated cases have been diagnosed in 2017. Of these, 8 are confirmed cases including:
- 6 cases with virus detected [PCR positive]
- 2 cases with antibody evidence indicating recent infection [seroconversion]
and 6 cases with antibody evidence highly indicative of recent infection (Zika-specific IgM) [probable cases].
So far in 2017, no cases have been diagnosed in pregnant women.
3.1 Region of travel for Zika cases diagnosed in UK travellers 2015-2017
|Region of travel||2015||2016||2017||Total|
|More than one region||1||4||1||6|
|Total travel associated cases||4||283||14||301|
|Total travel associated cases in pregnant women||-||7||-||7|
*The cases acquired in North America had travelled to 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.
3.2 Non travel-associated cases in UK: 2015-2017
|Non travel-associated cases||2015||2016||2017||Total|
|Likely sexual transmission||-||1||-||1|
4. WHO Emergency Committee declaration
The WHO International Health Regulations (IHR) Emergency Committee (EC) 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.
On 18 November 2016, the EC felt that Zika virus and its associated consequences remained 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 declared the end to the PHEIC.
The WHO 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 have been incorporated into a longer term response mechanism already outlined in the WHO Zika Strategic Response Plan.