The outbreak of Zika virus infection first reported in December’s edition of EPI-Insight, is continuing to spread in the Americas and Caribbean, and to emerge in countries previously unaffected by the virus (Volume 17 Issue 3). On February 1^st 2016, the World Health Organization (WHO) declared the Zika outbreak to be a Public Health Emergency of International Concern (PHEIC), following the first meeting of the Emergency Committee convened by the Director-General under International Health Regulations (IHR). A PHEIC was declared because of the rapidity of spread of Zika virus infection, the initial association of Zika virus infection and microcephaly, and latterly the association of Zika virus infection and Guillain-Barré syndrome (GBS).(1)

Affected countries/territories

Autochthonous Zika cases have been reported in the Pacific region since the beginning of 2014 and in Brazil since April 2015. Between 1/1/2007 and 16/3/2016, the Pan American Health Organization (PAHO) is reporting that Zika virus infection has been documented in a total of 59 countries and territories. Geographical distribution of Zika virus has steadily expanded since the virus was first detected in the Americas (with extension into the Caribbean) in 2014. Autochthonous Zika virus transmission has been reported in 33 countries and territories of this region.

A list of countries reporting local transmission of confirmed Zika virus infections in the past nine months can be found on the HPSC website:

American Samoa, Aruba, Barbados, Bolivia, Bonaire, Brazil, Cape Verde, Colombia, Costa Rica, Cuba, Curacao, Dominica, Dominican Republic, Ecuador, El Salvador, Fiji, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Jamaica, Maldives, Marshall Islands, Martinique, Mexico, New Caledonia, Nicaragua, Panama, Paraguay, Philippines, Puerto Rico, Saint Martin, Saint Vincent and the Grenadines, Samoa, Sint Maarten, Solomon Islands, St Croix US Virgin Islands, Suriname, Thailand, Tonga, Trinidad and Tobago, Venezuela.  A full list of affected countries and their territories can be found on the ECDC website. 

Congenital CNS malformations

An observed ecological association between Zika virus infection in pregnancy and foetal microcephaly have been under investigation since October 2015, when first reported in the northeast of the country by the Brazilian Ministry of Health. The observed increase in microcephaly and other foetal malformations, and its co-occurrence with an extensive Zika virus infection epidemic has been reported in Brazil and French Polynesia, while two additional exported cases linked to a stay in Brazil have been identified in the United States of America and Slovenia.

On February 17, Brazil’s Ministry of Health announced a joint case control study was being undertaken with CDC, to determine the risk of microcephaly in mothers with confirmed Zika infection. In addition, a possible association between ZVD and Guillain-Barré syndrome (GBS) is also being investigated. 

The strong spatio-temporal association between Zika virus infection and microcephaly that has been seen in Brazil and French Polynesia would certainly suggest the potential for a causal relationship.(2) However, a number of authors have begun to look at this relationship in terms of formal causality, and while acknowledging the strength of the association (sufficiently strong to ensure that the core public health messages for pregnant women or women of childbearing age to defer travel or, practice safe sex if they or their partners have travelled to affected areas were prudent health messages to promote and should remain in place), that suggest that there is a need to produce stronger evidence before the relationship can truly be considered causal.(3)  The difficulty in proving a link between Zika virus infection and birth defects is complicated by the fact that relatively little is known about Zika; there is no easy-to-use test to diagnose infection; and there is some disagreement as to the most valid manner by which to define microcephaly.(4)

Since the beginning of this epidemic in 2015, three cases of imported ZVD have been identified in Ireland (two from Colombia, in 2015 and 2016 and one from Barbados, in 2015).

ECDC’s most recent Rapid Risk Assessment of March 9^th 2016, outlines the current situation, documenting the numbers of CNS malformation and GBS from the affected countries.

The Scientific Advisory Committee of the Health Protection Surveillance Centre has established a Zika virus infection Subcommittee with relevant, microbiological, infectious disease, obstetrics, paediatric, public health and environmental health experts to monitor the situation and oversee the development of guidance relevant to this outbreak. The SAC Zika virus infection Subcommittee has met on two occasions; the next meeting is scheduled to take place on April 11^th, 2016.

Communication strategies and messages have been developed to minimise the potential for infection in Irish citizens travelling to affected countries.  The key risk groups are pregnant women or women at risk of becoming pregnant.  

The primary transmission pathway for ZVD is through biting, infected mosquitoes; HPSC has general advice on minimising the likelihood of being bitten by mosquitoes. Further specific guidance  that women can take to prevent themselves being bitten is also available on the HPSC website. As Zika virus can be transmitted sexually via semen, especially if the male partner developed symptoms of Zika virus infection. From a precautionary point of view, women are being advised to practice safe sex with a partner who has recently returned from an affected area:

A sexual partner who has not had any symptoms of Zika:

• Practice safe sex (by wearing a condom) for a period of 1 month after return from a Zika affected area.

A sexual partner who developed symptoms that could be due to Zika (fever, headache, aches, pains, rash, itchy eyes):

• Practice safe sex (by wearing a condom) for 6 months following start of his symptoms.

In addition, for women who are pregnant or trying to become pregnant, it is being recommended that they should consider postponing their travel to affected areas. If travel is considered unavoidable, the person should consult their doctor or seek advice from a travel clinic two months before travelling to a country affected by Zika virus. In addition, such women, if travelling to an affected area, should practice scrupulous mosquito bite prevention and to practice safe sex (by the use of condoms) for the duration of their stay as there is no treatment to cure Zika virus infection and there is no vaccine to prevent development of Zika virus infection.

Further information is available in the Zika virus infection section of the HPSC website.