Active Zika Virus Transmission Research Articles

Nation-wide vector surveillance on Zika and Dengue did not indicate transmission of the American lineage-pandemic Zika virus in India

ObjectivesFollowing the Public Health Emergency of International Concern declared on Zika by the World Health Organization during 2016, the Indian Council of Medical Research carried out nationwide vector surveillance for Zika and Dengue viruses (ZIKV and DENV) in India as a preparedness measure in 2016–19. MethodsHigh-risk zones distributed to 49 Districts in 14 states/union territories were included in the study. Seven ICMR institutions participated, following a standard operating protocol. Aedes specimens sampled weekly were processed by multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) for ZIKV/DENV and random samples crosschecked with real-time RT-PCR for ZIKV. ResultsAltogether, 79 492 Aedes specimens in 6492 pools were processed; 3 (0.05%) and 63 (0.97%) pools, respectively, were found positive for ZIKV and DENV. ZIKV infections were recorded in Aedes aegypti sampled during the 2018 sporadic Zika outbreak in Jaipur, Rajasthan. However, these belonged to the Asian lineage of the virus, already circulating in the country. Both Ae. aegypti and Aedes albopictus distributed to 8 states/union territories were found to be infected with DENV. Both sexes of Ae. albopictus were infected, indicating transovarial transmission. ConclusionThis investigation evinced no active transmission of the American lineage-pandemic Zika virus in India during the pandemic period.

Preventive effects of folic acid on Zika virus-associated poor pregnancy outcomes in immunocompromised mice.

Zika virus (ZIKV) infection may lead to congenital microcephaly and pregnancy loss in pregnant women. In the context of pregnancy, folic acid (FA) supplementation may reduce the risk of abnormal pregnancy outcomes. Intriguingly, FA may have a beneficial effect on the adverse pregnancy outcomes associated with ZIKV infection. Here, we show that FA inhibits ZIKV replication in human umbilical vein endothelial cells (HUVECs) and a cell culture model of blood-placental barrier (BPB). The inhibitory effect of FA against ZIKV infection is associated with FRα-AMPK signaling. Furthermore, treatment with FA reduces pathological features in the placenta, number of fetal resorptions, and stillbirths in two mouse models of in utero ZIKV transmission. Mice with FA treatment showed lower viral burden and better prognostic profiles in the placenta including reduced inflammatory response, and enhanced integrity of BPB. Overall, our findings suggest the preventive role of FA supplementation in ZIKV-associated abnormal pregnancy and warrant nutritional surveillance to evaluate maternal FA status in areas with active ZIKV transmission.

Local Transmission of Zika Virus in Miami-Dade County: The Florida Department of Health Rises to the Challenge.

As early as 2015, Florida and Centers for Disease Control and Prevention (CDC) public health officials recognized the potential danger of Zika for US residents and visitors. The Zika virus, a mosquito-borne flavivirus, is transmitted through the bite of the Aedes aegypti mosquito. A physician in Miami-Dade notified the Florida Department of Health (DOH) of the first non-travel-related Zika case in the United States. A 23-year old pregnant woman had presented on July 7, 2016, at 23 weeks of gestation, with a 3-day history of fever, widespread pruritic rash, and sore throat. Three more cases, involving men, were reported in Dade and Broward counties. These notifications set into motion additional activities from the DOH's Zika Playbook: increased mosquito surveillance; collaboration with the CDC on recommendations for mosquito abatement techniques; and increased awareness of the risks of Zika. In August, the department reported that active transmission of Zika virus was occurring in one small area in Miami-Dade County known as Wynwood. Mosquito trapping in the area with local transmission identified large numbers of the Zika vector, Aedes aegypti females and a large number of mosquito larval sites. Control efforts included larviciding, eliminating standing water, and backpack and truck spraying of insecticides. A communication strategy was developed that addressed risk mitigation, public concerns over application of noxious pesticides, loss of tourist revenue, and reproductive issues. It was reported on December 28, 2016, that there had been 256 locally acquired cases of infection of Zika, 1011 travel-related cases, and 208 pregnant women with laboratory evidence of Zika. At the end of 2018, 2 years after active Zika virus transmission was controlled in Florida, there have been 101 reported cases of Zika during 2018 but none have been linked to local transmission.

Zika transmission patterns: a meta-review.

To assesses what is known and identify knowledge gaps for Zika virus (ZIKV) transmission patterns. Meta-review searching the databases BioSys; Cochrane Infectious Diseases Group Specialised Register and Cochrane Central Register of Controlled Trials; EMBASE; Google Scholar; LILACS; MEDLINE (PubMed); Web of Science; and WHOLIS with the term 'ZIKA'. Systematic reviews and reviews specifying the search methods and describing potential modes of transmission were eligible for analysis. Of 5,401 hits for 'Zika', 44 studies were assessed and 11 included after applying in- and exclusion criteria: six systematic reviews and five reviews with specified methods, covering all ways of possible transmission. Results can be grouped into transmission routes with good evidence and agreement between the studies (evidence on vector, mother-to-child and sexual transmission) and transmission routes with limited evidence. Transmission by breastfeeding, intrapartum, by animal bites or laboratory-based remains inconclusive, as these routes are suggested by single studies only. The risk of transfusion transmission is described and public health measures for safe transfusion should be taken as available. Our results imply the need for public health measures to limit transmission via vectors, mother-to-child, sexual transmission and blood transfusion. Also needed are long-term prospective cohort studies covering periods of active Zika virus transmission and measuring epidemiological parameters to establish evidence on other routes of transmission; seroprevalence studies; transmission dynamics modelling and modelling health impacts by different modes of transmission.

High infection rate of Zika virus in mosquitoes collected from an area of active Zika virus transmission in eastern Thailand

High infection rate of Zika virus in mosquitoes collected from an area of active Zika virus transmission in eastern Thailand

Sleep EEG of Microcephaly in Zika Outbreak

ABSTRACTMicrocephaly (MC), previously considered rare, is now a health emergency of international concern because of the devastating Zika virus pandemic outbreak of 2015. The authors describe the electroencephalogram (EEG) findings in sleep EEG of epileptic children who were born with microcephaly in areas of Brazil with active Zika virus transmission between 2014 and 2017. The authors reviewed EEGs from 23 children. Nine were females (39.2%), and the age distribution varied from 4 to 48 months. MC was associated with mother positive serology to toxoplasmosis (toxo), rubella (rub), herpes, and dengue (1 case); toxo (1 case); chikungunya virus (CHIKV) (1 case); syphilis (1 case); and Zika virus (ZIKV) (10 cases). In addition, 1 case was associated with perinatal hypoxia and causes of 9 cases remain unknown. The main background EEG abnormality was diffuse slowing (10 cases), followed by classic (3 cases) and modified (5 cases) hypsarrhythmia. A distinct EEG pattern was seen in ZIKV (5 cases), toxo (2 cases), and undetermined cause (1 case). It was characterized by runs of frontocentrotemporal 4.5–13 Hz activity (7 cases) or diffuse and bilateral runs of 18–24 Hz (1 case). In ZIKV, this rhythmic activity was associated with hypsarrhythmia or slow background. Further studies are necessary to determine if this association is suggestive of ZIKV infection. The authors believe that EEG should be included in the investigation of all newly diagnosed congenital MC, especially those occurring in areas of autochthonous transmission of ZIKV.

Establishing a Timeline to Discontinue Routine Testing of Asymptomatic Pregnant Women for Zika Virus Infection - American Samoa, 2016-2017.

The first patients with laboratory-confirmed cases of Zika virus disease in American Samoa had symptom onset in January 2016 (1). In response, the American Samoa Department of Health (ASDoH) implemented mosquito control measures (1), strategies to protect pregnant women (1), syndromic surveillance based on electronic health record (EHR) reports (1), Zika virus testing of persons with one or more signs or symptoms of Zika virus disease (fever, rash, arthralgia, or conjunctivitis) (1-3), and routine testing of all asymptomatic pregnant women in accordance with CDC guidance (2,3). All collected blood and urine specimens were shipped to the Hawaii Department of Health Laboratory for Zika virus testing and to CDC for confirmatory testing. Early in the response, collection and testing of specimens from pregnant women was prioritized over the collection from symptomatic nonpregnant patients because of limited testing and shipping capacity. The weekly numbers of suspected Zika virus disease cases declined from an average of six per week in January-February 2016 to one per week in May 2016. By August, the EHR-based syndromic surveillance (1) indicated a return to pre-outbreak levels. The last Zika virus disease case detected by real-time, reverse transcription-polymerase chain reaction (rRT-PCR) occurred in a patient who had symptom onset on June 19, 2016. In August 2016, ASDoH requested CDC support in assessing whether local transmission had been reduced or interrupted and in proposing a timeline for discontinuation of routine testing of asymptomatic pregnant women. An end date (October 15, 2016) was determined for active mosquito-borne transmission of Zika virus and a timeline was developed for discontinuation of routine screening of asymptomatic pregnant women in American Samoa (conception after December 10, 2016, with permissive testing for asymptomatic women who conceive through April 15, 2017).

Seven Cases of Zika Virus Infection in South Florida.

IntroductionZika virus, an arbovirus of the Flaviviridae family, is a mosquito-borne virus known to cause microcephaly through vertical transmission. Infection presents with mild, self-limiting symptoms. Currently, a Zika virus outbreak has spread across most of South and Central America. Travel-related and sexually transmitted cases have been reported across the United States. However, the vector-borne transmission has been limited to Florida and Texas. We present seven cases of Zika virus infection that presented at a single institution in South Florida.MethodsPatients were included that had real-time polymerase-chain reaction (RT-PCR) for Zika virus RNA in urine or serum or enzyme-linked immunosorbent assay (ELISA) for Immunoglobulin M (IgM) antibody against Zika virus in serum.ResultsAll seven patients reported recent travel or employment in areas of active Zika virus transmission and at least two of the four most commonly reported symptoms (fever, arthralgia, rash, and conjunctivitis) with a rash present in all patients. All patients had positive RT-PCR for Zika virus RNA in urine. RT-PCR for Zika virus RNA in serum was negative in four of five patients that were tested, indicating that these patients likely presented one to two weeks after symptom onset.ConclusionThe future of Zika virus outbreaks in other cities in the United States is still uncertain. However, it is clear that prevention and control policies are urgently needed. We have presented seven confirmed cases of Zika virus infection in South Florida. In addition to conducting research concerning both the diagnostic and therapeutic aspects of the virus, there is a need for public awareness of its presentation, methods of transmission, and subsequent clinical outcomes.

A Pregnant Teen Living in an Area With Active Zika Virus Transmission

“For the past week or so during the night I feel hot and then I feel chilled. This morning I saw a rash on my face and stomach,” stated a 16-year-old female patient at a visit to her local health clinic. The patient, at 20 weeks' gestation, is halfway through her first pregnancy. She had been in her usual good state of health until 1 week ago, when she noticed mild, flu-like symptoms. Jane Cox, Director of Nursing, NCH Community Home Care, Naples, FL.

Using a call center to coordinate Zika virus testing-New York City, 2016.

After local testing criteria for Zika virus expanded to include asymptomatic pregnant women who traveled to areas with active Zika virus transmission while pregnant, the New York City (NYC) Department of Health and Mental Hygiene (DOHMH) experienced a surge in test requests and subsequent testing delays due to factors such as incorrectly completed laboratory requisition forms. The authors describe how DOHMH addressed these issues by establishing the Zika Testing Call Center (ZTCC). Using a case study approach, the authors illustrate how DOHMH leveraged protocols, equipment, and other resources used previously during DOHMH&s Ebola emergency response to meet NYC's urgent Zika virus testing needs. To request Zika virus testing, providers call the ZTCC; if patients meet testing criteria, the ZTCC collects data necessary to complete requisition forms and sends the forms back to providers. The ZTCC also provides guidance on specimens needed for Zika virus testing. Providers submit completed requisition forms and appropriate specimens to DOHMH for testing. During March 21 through July 21, 2016, testing for 3,866 patients was coordinated through the ZTCC. The ZTCC exemplifies how a health department, using previous emergency response experiences, can quickly address local testing needs for an emerging infectious disease.

Preparedness for Zika Virus Disease - New York City, 2016.

The rapid spread of Zika virus across the World Health Organization's Region of the Americas has had a direct effect on the U.S. health care delivery system. Hospitals in New York City (NYC) have been implementing prevention and response efforts consistent with CDC guidance. As of September 21, 2016, a total of 715 cases of laboratory-confirmed Zika virus disease had been diagnosed in New York state among travelers who returned from affected areas, their sexual contacts, or infants infected in utero. This represents the highest number of reported cases in any state to date, and underscores the importance of health care systems preparing to care for patients with possible Zika virus disease (1). Building upon a framework that was established in 2014 to screen patients for possible exposure to Ebola virus disease (Ebola), NYC Health + Hospitals,* the largest municipal health care delivery system in the United States, implemented a Zika Preparedness and Response Action Plan† (Zika Action Plan) to address the threat from Zika and ensure appropriate patient care. The plan developed by NYC Health + Hospitals includes universal travel screening, signage depicting areas with active Zika virus transmission, clinical and epidemiologic evaluation for possible Zika virus exposure, diagnostic testing for Zika virus infection and linking of infected patients to appropriate specialists, and education on Zika virus disease and preventive measures (e.g., avoiding travel to areas with active Zika virus transmission).

Update: Interim Guidance for Preconception Counseling and Prevention of Sexual Transmission of Zika Virus for Persons with Possible Zika Virus Exposure - United States, September 2016.

CDC has updated its interim guidance for persons with possible Zika virus exposure who are planning to conceive (1) and interim guidance to prevent transmission of Zika virus through sexual contact (2), now combined into a single document. Guidance for care for pregnant women with possible Zika virus exposure was previously published (3). Possible Zika virus exposure is defined as travel to or residence in an area of active Zika virus transmission (http://www.cdc.gov/zika/geo/index.html), or sex* without a condom† with a partner who traveled to or lived in an area of active transmission. Based on new though limited data, CDC now recommends that all men with possible Zika virus exposure who are considering attempting conception with their partner, regardless of symptom status,§ wait to conceive until at least 6 months after symptom onset (if symptomatic) or last possible Zika virus exposure (if asymptomatic). Recommendations for women planning to conceive remain unchanged: women with possible Zika virus exposure are recommended to wait to conceive until at least 8 weeks after symptom onset (if symptomatic) or last possible Zika virus exposure (if asymptomatic). Couples with possible Zika virus exposure, who are not pregnant and do not plan to become pregnant, who want to minimize their risk for sexual transmission of Zika virus should use a condom or abstain from sex for the same periods for men and women described above. Women of reproductive age who have had or anticipate future Zika virus exposure who do not want to become pregnant should use the most effective contraceptive method that can be used correctly and consistently. These recommendations will be further updated when additional data become available.

Guillain-Barré Syndrome During Ongoing Zika Virus Transmission - Puerto Rico, January 1-July 31, 2016.

Guillain-Barré syndrome (GBS) is a postinfectious autoimmune disorder characterized by bilateral flaccid limb weakness attributable to peripheral nerve damage (1). Increased GBS incidence has been reported in countries with local transmission of Zika virus, a flavivirus transmitted primarily by certain Aedes species mosquitoes (2). In Puerto Rico, three arthropod-borne viruses (arboviruses) are currently circulating: Zika, dengue, and chikungunya. The first locally acquired Zika virus infection in Puerto Rico was reported in December 2015 (3). In February 2016, the Puerto Rico Department of Health (PRDH), with assistance from CDC, implemented the GBS Passive Surveillance System (GBPSS) to identify new cases of suspected GBS (4). Fifty-six suspected cases of GBS with onset of neurologic signs during January 1-July 31, 2016, were identified. Thirty-four (61%) patients had evidence of Zika virus or flavivirus infection; the median age of these patients was 55 years (range=21-88 years), and 20 (59%) patients were female. These 34 patients were residents of seven of eight PRDH public health regions. All 34 patients were hospitalized and treated with intravenous immunoglobulin G (IVIg), the standard treatment for GBS; 21 (62%) required intensive care unit admission, including 12 (35%) who required endotracheal intubation and mechanical ventilation. One patient died of septic shock after treatment for GBS. Additionally, 26 cases of neurologic conditions other than GBS were reported through GBPSS, including seven (27%) in patients with evidence of Zika virus or flavivirus infection. Residents of and travelers to Puerto Rico and countries with active Zika virus transmission should follow recommendations for prevention of Zika virus infections.* Persons with signs or symptoms consistent with GBS should promptly seek medical attention. Health care providers in areas with ongoing local transmission seeing patients with neurologic illnesses should consider GBS and report suspected cases to public health authorities.

Update: Interim Guidance for Health Care Providers Caring for Pregnant Women with Possible Zika Virus Exposure - United States, July 2016.

CDC has updated its interim guidance for U.S. health care providers caring for pregnant women with possible Zika virus exposure, to include the emerging data indicating that Zika virus RNA can be detected for prolonged periods in some pregnant women. To increase the proportion of pregnant women with Zika virus infection who receive a definitive diagnosis, CDC recommends expanding real-time reverse transcription-polymerase chain reaction (rRT-PCR) testing. Possible exposures to Zika virus include travel to or residence in an area with active Zika virus transmission, or sex* with a partner who has traveled to or resides in an area with active Zika virus transmission without using condoms or other barrier methods to prevent infection.(†) Testing recommendations for pregnant women with possible Zika virus exposure who report clinical illness consistent with Zika virus disease(§) (symptomatic pregnant women) are the same, regardless of their level of exposure (i.e., women with ongoing risk for possible exposure, including residence in or frequent travel to an area with active Zika virus transmission, as well as women living in areas without Zika virus transmission who travel to an area with active Zika virus transmission, or have unprotected sex with a partner who traveled to or resides in an area with active Zika virus transmission). Symptomatic pregnant women who are evaluated <2 weeks after symptom onset should receive serum and urine Zika virus rRT-PCR testing. Symptomatic pregnant women who are evaluated 2-12 weeks after symptom onset should first receive a Zika virus immunoglobulin (IgM) antibody test; if the IgM antibody test result is positive or equivocal, serum and urine rRT-PCR testing should be performed. Testing recommendations for pregnant women with possible Zika virus exposure who do not report clinical illness consistent with Zika virus disease (asymptomatic pregnant women) differ based on the circumstances of possible exposure. For asymptomatic pregnant women who live in areas without active Zika virus transmission and who are evaluated <2 weeks after last possible exposure, rRT-PCR testing should be performed. If the rRT-PCR result is negative, a Zika virus IgM antibody test should be performed 2-12 weeks after the exposure. Asymptomatic pregnant women who do not live in an area with active Zika virus transmission, who are first evaluated 2-12 weeks after their last possible exposure should first receive a Zika virus IgM antibody test; if the IgM antibody test result is positive or equivocal, serum and urine rRT-PCR should be performed. Asymptomatic pregnant women with ongoing risk for exposure to Zika virus should receive Zika virus IgM antibody testing as part of routine obstetric care during the first and second trimesters; immediate rRT-PCR testing should be performed when IgM antibody test results are positive or equivocal. This guidance also provides updated recommendations for the clinical management of pregnant women with confirmed or possible Zika virus infection. These recommendations will be updated when additional data become available.

Update: Interim Guidance for Prevention of Sexual Transmission of Zika Virus - United States, July 2016.

Zika virus has been identified as a cause of congenital microcephaly and other serious brain defects (1). CDC issued interim guidance for the prevention of sexual transmission of Zika virus on February 5, 2016, with an initial update on April 1, 2016 (2). The following recommendations apply to all men and women who have traveled to or reside in areas with active Zika virus transmission* and their sex partners. The recommendations in this report replace those previously issued and are now updated to reduce the risk for sexual transmission of Zika virus from both men and women to their sex partners. This guidance defines potential sexual exposure to Zika virus as having had sex with a person who has traveled to or lives in an area with active Zika virus transmission when the sexual contact did not include a barrier to protect against infection. Such barriers include male or female condoms for vaginal or anal sex and other barriers for oral sex.(†) Sexual exposure includes vaginal sex, anal sex, oral sex, or other activities that might expose a sex partner to genital secretions.(§) This guidance will be updated as more information becomes available.

Survey of Blood Collection Centers and Implementation of Guidance for Prevention of Transfusion-Transmitted Zika Virus Infection — Puerto Rico, 2016

Since November 2015, Puerto Rico has reported active mosquito-borne transmission of Zika virus. Because of the potential for Zika virus to be transmitted through transfusion of blood components, and because a high percentage of persons infected with Zika virus are asymptomatic, the Food and Drug Administration (FDA) recommended that blood collections cease in areas of the United States affected by active vector-borne transmission of Zika virus until laboratory screening of blood donations or pathogen reduction technology (PRT) for treatment of blood components can be implemented. To inform efforts to maintain the safety and availability of the blood supply in Puerto Rico, CDC, in collaboration with the Puerto Rico Department of Health, conducted a rapid assessment of blood collection and use on the island. A total of 139,369 allogeneic red blood cell (RBC) units, 45,243 platelet units, and 56,466 plasma units were collected in or imported to Puerto Rico during 2015, and 135,966 allogeneic RBC units, 13,526 therapeutic platelet units, and 25,775 plasma units were transfused. Because of the potential for local Zika virus transmission in areas with a competent mosquito vector, other areas of the United States should develop plans to ensure local blood safety and adequacy. Blood collection organizations and public health agencies should collaborate to maintain the safety and availability of local blood supplies in accordance with FDA guidance.

Zika Virus Surveillance and Preparedness - New York City, 2015-2016.

Zika virus has rapidly spread through the World Health Organization's Region of the Americas since being identified in Brazil in early 2015. Transmitted primarily through the bite of infected Aedes species mosquitoes, Zika virus infection during pregnancy can cause spontaneous abortion and birth defects, including microcephaly (1,2). New York City (NYC) is home to a large number of persons who travel frequently to areas with active Zika virus transmission, including immigrants from these areas. In November 2015, the NYC Department of Health and Mental Hygiene (DOHMH) began developing and implementing plans for managing Zika virus and on February 1, 2016, activated its Incident Command System. During January 1-June 17, 2016, DOHMH coordinated diagnostic laboratory testing for 3,605 persons with travel-associated exposure, 182 (5.0%) of whom had confirmed Zika virus infection. Twenty (11.0%) confirmed patients were pregnant at the time of diagnosis. In addition, two cases of Zika virus-associated Guillain-Barré syndrome were diagnosed. DOHMH's response has focused on 1) identifying and diagnosing suspected cases; 2) educating the public and medical providers about Zika virus risks, transmission, and prevention strategies, particularly in areas with large populations of immigrants from areas with ongoing Zika virus transmission; 3) monitoring pregnant women with Zika virus infection and their fetuses and infants; 4) detecting local mosquito-borne transmission through both human and mosquito surveillance; and 5) modifying existing Culex mosquito control measures by targeting Aedes species of mosquitoes through the use of larvicides and adulticides.

Zika Virus Infection: Current Concerns and Perspectives.

The Zika virus outbreaks highlight the growing importance need for a reliable, specific and rapid diagnostic device to detect Zika virus, as it is often recognized as a mild disease without being identified. Many Zika virus infection cases have been misdiagnosed or underreported because of the non-specific clinical presentation. The aim of this review was to provide a critical and comprehensive overview of the published peer-reviewed evidence related to clinical presentations, various diagnostic methods and modes of transmission of Zika virus infection, as well as potential therapeutic targets to combat microcephaly. Zika virus is mainly transmitted through bites from Aedes aegypti mosquito. It can also be transmitted through blood, perinatally and sexually. Pregnant women are advised to postpone or avoid travelling to areas where active Zika virus transmission is reported, as this infection is directly linked to foetal microcephaly. Due to the high prevalence of Guillain-Barre syndrome and microcephaly in the endemic area, it is vital to confirm the diagnosis of Zika virus. Zika virus infection had been declared as a public health emergency and of international concern by the World Health Organisation. Governments and agencies should play an important role in terms of investing time and resources to fundamentally understand this infection so that a vaccine can be developed besides raising awareness.

Patterns in Zika Virus Testing and Infection, by Report of Symptoms and Pregnancy Status - United States, January 3-March 5, 2016.

CDC recommends Zika virus testing for potentially exposed persons with signs or symptoms consistent with Zika virus disease, and recommends that health care providers offer testing to asymptomatic pregnant women within 12 weeks of exposure. During January 3-March 5, 2016, Zika virus testing was performed for 4,534 persons who traveled to or moved from areas with active Zika virus transmission; 3,335 (73.6%) were pregnant women. Among persons who received testing, 1,541 (34.0%) reported at least one Zika virus-associated sign or symptom (e.g., fever, rash, arthralgia, or conjunctivitis), 436 (9.6%) reported at least one other clinical sign or symptom only, and 2,557 (56.4%) reported no signs or symptoms. Among 1,541 persons with one or more Zika virus-associated symptoms who received testing, 182 (11.8%) had confirmed Zika virus infection. Among the 2,557 asymptomatic persons who received testing, 2,425 (94.8%) were pregnant women, seven (0.3%) of whom had confirmed Zika virus infection. Although risk for Zika virus infection might vary based on exposure-related factors (e.g., location and duration of travel), in the current setting in U.S. states, where there is no local transmission, most asymptomatic pregnant women who receive testing do not have Zika virus infection.

Survey of Blood Collection Centers and Implementation of Guidance for Prevention of Transfusion-Transmitted Zika Virus Infection--Puerto Rico, 2016.

Since November 2015, Puerto Rico has reported active mosquito-borne transmission of Zika virus. Because of the potential for Zika virus to be transmitted through transfusion of blood components, and because a high percentage of persons infected with Zika virus are asymptomatic, the Food and Drug Administration (FDA) recommended that blood collections cease in areas of the United States affected by active vector-borne transmission of Zika virus until laboratory screening of blood donations or pathogen reduction technology (PRT) for treatment of blood components can be implemented. To inform efforts to maintain the safety and availability of the blood supply in Puerto Rico, CDC, in collaboration with the Puerto Rico Department of Health, conducted a rapid assessment of blood collection and use on the island. A total of 139,369 allogeneic red blood cell (RBC) units, 45,243 platelet units, and 56,466 plasma units were collected in or imported to Puerto Rico during 2015, and 135,966 allogeneic RBC units, 13,526 therapeutic platelet units, and 25,775 plasma units were transfused. Because of the potential for local Zika virus transmission in areas with a competent mosquito vector, other areas of the United States should develop plans to ensure local blood safety and adequacy. Blood collection organizations and public health agencies should collaborate to maintain the safety and availability of local blood supplies in accordance with FDA guidance.