Use of Blood Donor Screening Data to Estimate Zika Virus Incidence, Puerto Rico, April-August 2016.

Puerto Rico has been heavily impacted by Zika virus, a mosquitoborne flavivirus that emerged in the Americas during 2015. Although most persons with Zika virus show no symptoms, the virus can cause neurologic and other complications, including fetal microcephaly. Local Zika virus transmission in Puerto Rico has been reported since December 2015. To prevent transfusion-associated transmission, local blood collection ceased in March 2016 but resumed in April 2016 after Zika virus screening of blood donations became available. Using data from screening of blood donations collected by the 2 largest blood centers in Puerto Rico during April 3-August 12, 2016, and assuming a 9.9-day duration of viremia, we estimated that 469,321 persons in Puerto Rico were infected during this period, for an estimated cumulative incidence of 12.9%. Results from blood donation screening during arboviral outbreaks can supplement routine clinical and surveillance data for improved targeting of prevention efforts.

Screening of Blood Donations for Zika Virus Infection - Puerto Rico, April 3-June 11, 2016.

Transfusion-transmitted infections have been documented for several arboviruses, including West Nile and dengue viruses (1). Zika virus, a flavivirus transmitted primarily by Aedes aegypti mosquitoes that has been identified as a cause of congenital microcephaly and other serious brain defects (2), became recognized as a potential threat to blood safety after reports from a 2013-2014 outbreak in French Polynesia. Blood safety concerns were based on very high infection incidence in the population at large during epidemics, the high percentage of persons with asymptomatic infection, the high proportion of blood donations with evidence of Zika virus nucleic acid upon retrospective testing, and an estimated 7-10-day period of viremia (3). At least one instance of transfusion transmission of Zika virus has been documented in Brazil after the virus emerged there, likely in 2014 (4). Rapid epidemic spread has followed to other areas of the Americas, including Puerto Rico.