As of 10 August 2016, 69 countries and territories (Fig. 1, Table 1) have reported evidence of mosquito-borne Zika virus transmission since 2007 (66 of these countries and territories have reported evidence of mosquito-borne Zika virus transmission since 2015):
- 52 countries and territories with a first reported outbreak from 2015 onwards (Table 1).
- Four countries are classified as having possible endemic transmission or have reported evidence of local mosquito-borne Zika infections in 2016.
- 13 countries and territories have reported evidence of local mosquito-borne Zika infections in or before 2015, but without documentation of cases in 2016, or with the outbreak terminated.
The Cayman Islands, a British Overseas Territory in the Caribbean, is the latest territory to report locally-acquired mosquito borne Zika virus infection.
Since February 2016, 11 countries have reported evidence of person-to-person transmission of Zika virus, probably via a sexual route (Table 2).
As of 10 August 2016, 15 countries or territories have reported microcephaly and other central nervous system (CNS) malformations potentially associated with Zika virus infection or suggestive of congenital infection. Canada is the latest country to report a case of congenital malformation associated with a travel-related case of Zika virus infection. Four of the 15 total countries reported microcephaly cases born from mothers in countries with no endemic Zika virus transmission but who reported recent travel history to Zika-affected countries in the WHO Region of the Americas (Table 3).
As of 10 August 2016, the United States Centers for Disease Control and Prevention (USCDC) reported 15 live-born infants with birth defects and six pregnancy losses with birth defects with laboratory evidence of Zika virus infection.
As of 10 August 2016, 16 countries and territories worldwide have reported an increased incidence of Guillain-Barré syndrome (GBS) and/or laboratory confirmation of a Zika virus infection among GBS cases (Table 4). Grenada is the latest country to report a case of GBS associated with a confirmed Zika virus infection.
In Guinea-Bissau, on 29 June 2016, Institute Pasteur Dakar (IPD) laboratory technicians confirmed that three of 12 samples tested positive for Zika by PC-R. All 12 samples tested negative against IgM Zika. One additional sample from a recent case also tested positive for Zika virus infection. All four samples were sent to IPD on 1 July for gene sequencing and the results are pending. Results from the 22 additional samples collected from the Bijagos archipelago and sent to IPD are negative with ELISA and PCR testing. The same samples were also sent to Dakar for confirmation. A further total of 12 new samples were collected and results are still pending.
Two cases of microcephaly have been reported in the Western region of Gabu in GuineaBissau.
The family members of the two children with microcephaly have not travelled outside Guinea-Bissau. The investigations regarding these two cases are ongoing. Trainings for regional health staff on the Zika case definition and other areas are planned to help ensure that cases are detected efficiently and effectively.The joint mission by staff from the WHO Regional Office for Africa and from WHO headquarters to Guinea-Bissau has concluded and priority activities and gaps were identified as the following: additional financial resources to reinforce leadership and coordination mechanisms of the Emergency operations Centre (EOC); reinforcement of epidemiologic and entomologic surveillance systems; increasing laboratory capacity at three levels; strengthening of response to Zika cases in terms of detection, community involvement and risk communication; and continued monitoring of Zika virus and its complications.
Zika virus test kits have been made available by the local authorities at the Central Public Health Laboratory in Rio de Janeiro in Brazil and symptomatic athletes, volunteers, visitors and residents are encouraged to get tested.
WHO has developed advice and information on diverse topics in the context of Zika virus.
Risk assessment
Overall, the global risk assessment has not changed. Zika virus continues to spread geographically to areas where competent vectors are present. Although a decline in cases of Zika infection has been reported in some countries, or in some parts of countries, vigilance needs to remain high. At this stage, based on the evidence available, there is no overall decline in the outbreak.