Zika virus is transmitted primarily by mosquitoes of the genus Aedes. Most people infected with Zika virus do not develop symptoms; Zika virus infection during pregnancy is a cause of microcephaly and other congenital malformations in the infant, as well as preterm birth and miscarriage.
Zika virus infection is also associated with Guillain-Barré syndrome, neuropathy and myelitis in adults and children. In February 2016, the WHO declared Zika-related microcephaly a Public Health Emergency of International Concern (PHEIC) and the causal link between Zika virus and congenital malformations was confirmed. In November of the same year, the WHO declared the end of the PHEIC.
Although the number of Zika virus disease cases has dropped globally since 2017, transmission persists at low levels in several countries in the Americas and other endemic regions.
Zika virus infection cases in the US
With the publication of the document “Revised Recommendations for Reducing the Risk of Zika Virus Transmission by Blood and Blood Components, August 2016”, the North American Food and Drug Administration (FDA) recommended that measures for the prevention of transfusion transmission (via labile blood components) of Zika virus infection be strengthened in the United States of America (USA).
In 2015 and 2016, large outbreaks of Zika virus disease occurred in the Americas, resulting in increased travel-associated cases in the USA, widespread transmission in Puerto Rico and the US Virgin Islands, and limited local transmission in Florida and Texas. For this reason, the FDA recommended Nucleic Acid Testing (NAT) on blood and blood component donations for transfusion use, and authorised US blood banks to use tests still not fully validated for the biological qualification of donated blood.
In 2017, the number of reported cases of Zika virus disease in the United States began to decline. As of 2018, there have been no reported cases of Zika virus transmission from mosquito bites in mainland USA.
Zika virus infection in Italy
In Italy, the spread of Arboviruses, including Zika virus, is monitored through specific epidemiological surveillance programmes contained in the National Plan for Prevention, Surveillance and Response to Arboviruses (PNA) 2020-2025.
To date, Italy is to be considered a “non-endemic area for Zika virus as no locally transmitted cases of infection (autochthonous), but only imported cases (travellers from areas where the virus is circulating), have been recorded.
The Italian National Blood Centre (CNS) confirms the validity of the measures for the prevention of transfusion transmission of Zika virus infection already adopted in Italy. These are based on strengthening donor anamnestic surveillance (with particular reference to travel), and applying the criterion of the temporary suspension of donors who have stayed in areas considered at risk following reported autochthonous cases of Zika virus infection.
The CNS, in synergy with Italian national public health institutions, international blood authorities and the ECDC, constantly monitors the epidemiological situation and analyses the available scientific-based evidence so that it can update in real time the measures adopted to guarantee the quality and safety of blood donated by Italian donors.