Sustained Low-Level Transmission of Zika and Chikungunya Viruses after Emergence in the Fiji Islands.

Zika and chikungunya viruses were first detected in Fiji in 2015. Examining surveillance and phylogenetic and serologic data, we found evidence of low-level transmission of Zika and chikungunya viruses during 2013-2017, in contrast to the major outbreaks caused by closely related virus strains in other Pacific Island countries.

Ross River Virus Antibody Prevalence, Fiji Islands, 2013-2015.

A unique outbreak of Ross River virus (RRV) infection was reported in Fiji in 1979. In 2013, RRV seroprevalence among residents was 46.5% (362/778). Of the residents who were seronegative in 2013 and retested in 2015, 10.9% (21/192) had seroconverted to RRV, suggesting ongoing endemic circulation of RRV in Fiji.

The Use of Simple Laboratory Parameters in the Differential Diagnosis of Acute-Phase Zika and Dengue Viruses.

BACKGROUND: Differential diagnosis between acute-phase Zika and dengue is challenging because of a similar clinical presentation and the lack of available molecular diagnosis tools in most of endemic areas. OBJECTIVES: Our study aimed to evaluate the use of simple laboratory parameters to differentiate these infections. METHODS: We retrospectively compared simple hematology and biochemistry values in 81 and 341 patients with confirmed Zika and dengue, respectively, collected from June 2013 to March 2014 during the French Polynesia outbreaks. RESULTS: Thrombocytopenia, neutropenia, leukopenia, lymphopenia, and elevated aspartate aminotransaminases were significantly more frequent in dengue than in Zika (p < 0.001). Platelets <100 × 109/L, neutrophils <0.5 × 109/L, lymphocytes <0.5 × 109/L, and aspartate aminotransaminases >100 IU/mL were found in dengue but not in Zika. The positive predictive value of the -association of leukocytes <4 × 109/L + lymphocytes <1 × 109/L + aspartate aminotransaminases >40 IU/mL for the diagnosis of dengue was 90%, with an accuracy of 82.4%. CONCLUSION: For the differential diagnosis between acute-phase Zika and dengue, there is no specific standard laboratory pattern. We identified cutoff values and a combination of laboratory parameters that are a strong argument against Zika and in favor of dengue.

Zika Virus Infection during Pregnancy and Effects on Early Childhood Development, French Polynesia, 2013-2016.

Congenital Zika virus syndrome consists of a large spectrum of neurologic abnormalities seen in infants infected with Zika virus in utero. However, little is known about the effects of Zika virus intrauterine infection on the neurocognitive development of children born without birth defects. Using a case-control study design, we investigated the temporal association of a cluster of congenital defects with Zika virus infection. In a nested study, we also assessed the early childhood development of children recruited in the initial study as controls who were born without known birth defects,. We found evidence for an association of congenital defects with both maternal Zika virus seropositivity (time of infection unknown) and symptomatic Zika virus infection during pregnancy. Although the early childhood development assessment found no excess burden of developmental delay associated with maternal Zika virus infection, larger, longer-term studies are needed.

Seroprevalence of Dengue and Chikungunya Virus Antibodies, French Polynesia, 2014-2015.

We investigated dengue and chikungunya virus antibody seroprevalence in French Polynesia during 2014-2015. Dengue virus seroprevalence was ≈60% among schoolchildren and >83% among the general population; chikungunya virus seroprevalence was <3% before and 76% after Zika virus emergence (2013). Dengue virus herd immunity may affect Zika virus infection and pathogenesis.

An update on Zika virus infection.

The epidemic history of Zika virus began in 2007, with its emergence in Yap Island in the western Pacific, followed in 2013-14 by a larger epidemic in French Polynesia, south Pacific, where the first severe complications and non-vector-borne transmission of the virus were reported. Zika virus emerged in Brazil in 2015 and was declared a national public health emergency after local researchers and physicians reported an increase in microcephaly cases. In 2016, WHO declared the recent cluster of microcephaly cases and other neurological disorders reported in Brazil a global public health emergency. Similar clusters of microcephaly cases were also observed retrospectively in French Polynesia in 2014. In 2015-16, Zika virus continued its spread to cause outbreaks in the Americas and the Pacific, and the first outbreaks were reported in continental USA, Africa, and southeast Asia. Non-vector-borne transmission was confirmed and Zika virus was established as a cause of severe neurological complications in fetuses, neonates, and adults. This Review focuses on important updates and gaps in the knowledge of Zika virus as of early 2017.

Zika Virus.

Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) in the genus Flavivirus and the family Flaviviridae. ZIKV was first isolated from a nonhuman primate in 1947 and from mosquitoes in 1948 in Africa, and ZIKV infections in humans were sporadic for half a century before emerging in the Pacific and the Americas. ZIKV is usually transmitted by the bite of infected mosquitoes. The clinical presentation of Zika fever is nonspecific and can be misdiagnosed as other infectious diseases, especially those due to arboviruses such as dengue and chikungunya. ZIKV infection was associated with only mild illness prior to the large French Polynesian outbreak in 2013 and 2014, when severe neurological complications were reported, and the emergence in Brazil of a dramatic increase in severe congenital malformations (microcephaly) suspected to be associated with ZIKV. Laboratory diagnosis of Zika fever relies on virus isolation or detection of ZIKV-specific RNA. Serological diagnosis is complicated by cross-reactivity among members of the Flavivirus genus. The adaptation of ZIKV to an urban cycle involving humans and domestic mosquito vectors in tropical areas where dengue is endemic suggests that the incidence of ZIKV infections may be underestimated. There is a high potential for ZIKV emergence in urban centers in the tropics that are infested with competent mosquito vectors such as Aedes aegypti and Aedes albopictus.

History and Emergence of Zika Virus.

Zika virus was discovered in East Africa in 1947 by the Rockefeller Foundation during investigations on the ecology of yellow fever. Although it was subsequently shown to have widespread distribution in Africa and Asia, it was not known to cause epidemics until 2007. This paper describes the history of the virus discovery, emergence and evolution as an epidemic virus, and the its evolving clinical spectrum.

Ross River Virus Seroprevalence, French Polynesia, 2014-2015.

Ross River virus (RRV), spread by Aedes and Culex mosquitoes, is the most commonly transmitted arbovirus in Australia. A serosurvey of blood donors in French Polynesia during 2011-2013 suggested that RRV circulated without being detected. We report RRV circulation in French Polynesia based on further screening of blood samples collected during 2014-2015.

Zika Virus Seroprevalence, French Polynesia, 2014-2015.

During 2013-2014, French Polynesia experienced an outbreak of Zika virus infection. Serosurveys conducted at the end of the outbreak and 18 months later showed lower than expected disease prevalence rates (49%) and asymptomatic:symptomatic case ratios (1:1) in the general population but significantly different prevalence rates (66%) and asymptomatic:symptomatic ratios (1:2) in schoolchildren.

Guillain-Barré Syndrome outbreak associated with Zika virus infection in French Polynesia: a case-control study.

BACKGROUND: Between October, 2013, and April, 2014, French Polynesia experienced the largest Zika virus outbreak ever described at that time. During the same period, an increase in Guillain-Barré syndrome was reported, suggesting a possible association between Zika virus and Guillain-Barré syndrome. We aimed to assess the role of Zika virus and dengue virus infection in developing Guillain-Barré syndrome. METHODS: In this case-control study, cases were patients with Guillain-Barré syndrome diagnosed at the Centre Hospitalier de Polynésie Française (Papeete, Tahiti, French Polynesia) during the outbreak period. Controls were age-matched, sex-matched, and residence-matched patients who presented at the hospital with a non-febrile illness (control group 1; n=98) and age-matched patients with acute Zika virus disease and no neurological symptoms (control group 2; n=70). Virological investigations included RT-PCR for Zika virus, and both microsphere immunofluorescent and seroneutralisation assays for Zika virus and dengue virus. Anti-glycolipid reactivity was studied in patients with Guillain-Barré syndrome using both ELISA and combinatorial microarrays. FINDINGS: 42 patients were diagnosed with Guillain-Barré syndrome during the study period. 41 (98%) patients with Guillain-Barré syndrome had anti-Zika virus IgM or IgG, and all (100%) had neutralising antibodies against Zika virus compared with 54 (56%) of 98 in control group 1 (p<0.0001). 39 (93%) patients with Guillain-Barré syndrome had Zika virus IgM and 37 (88%) had experienced a transient illness in a median of 6 days (IQR 4-10) before the onset of neurological symptoms, suggesting recent Zika virus infection. Patients with Guillain-Barré syndrome had electrophysiological findings compatible with acute motor axonal neuropathy (AMAN) type, and had rapid evolution of disease (median duration of the installation and plateau phases was 6 [IQR 4-9] and 4 days [3-10], respectively). 12 (29%) patients required respiratory assistance. No patients died. Anti-glycolipid antibody activity was found in 13 (31%) patients, and notably against GA1 in eight (19%) patients, by ELISA and 19 (46%) of 41 by glycoarray at admission. The typical AMAN-associated anti-ganglioside antibodies were rarely present. Past dengue virus history did not differ significantly between patients with Guillain-Barré syndrome and those in the two control groups (95%, 89%, and 83%, respectively). INTERPRETATION: This is the first study providing evidence for Zika virus infection causing Guillain-Barré syndrome. Because Zika virus is spreading rapidly across the Americas, at risk countries need to prepare for adequate intensive care beds capacity to manage patients with Guillain-Barré syndrome. FUNDING: Labex Integrative Biology of Emerging Infectious Diseases, EU 7th framework program PREDEMICS. and Wellcome Trust.

Molecular detection of Zika virus in blood and RNA load determination during the French Polynesian outbreak.

Zika virus (ZIKV) viremia is reported as low and transient; however, these estimates rely on limited data. We report RNA loads in sera collected from symptomatic patients during the 2013-2014 French Polynesian ZIKV outbreak. We performed molecular detection of ZIKV RNA in sera from 747 patients presenting with suspected acute phase ZIKV infection. Among patients with confirmed infection, we analyzed the duration of viremia, assessed viral RNA loads and recorded the main clinical symptoms. A total of 210/747 (28.1%) sera tested positive using a ZIKV-specific RT-PCR. Viral RNA loads in symptomatic patients that ranged from 5 to 3.7 × 106 copies/mL (mean 9.9 × 104 copies/mL) were not related to a particular clinical presentation, and were significantly lower than those previously obtained from asymptomatic ZIKV infected blood donors. The rate of detection of ZIKV RNA in sera from suspected cases of acute phase ZIKV infection was low. ZIKV RNA loads were lower in symptomatic patients compared to asymptomatic blood donors and were lower than RNA loads usually reported in dengue infections. As there is no abrupt onset of symptoms in ZIKV infections, we suggest that infected patients sought for medical attention when viremia was already decreasing or had resolved.

Zika virus and blood transfusion: the experience of French Polynesia.

BACKGROUND: Between October 2013 and March 2014, French Polynesia experienced the largest Zika virus (ZIKV) outbreak ever described before the emergence of ZIKV in the Americas in 2015. As arbovirus transfusion-transmitted (TT) infections have been previously reported, we hypothesized that transfusion of blood products could also transmit ZIKV. STUDY DESIGN AND METHODS: Mitigation strategies to prevent ZIKV-TT infections included nonspecific measures and the implementation of a laboratory developed ZIKV-specific nucleic acid testing (NAT) assay. Donor sera were tested in pools of 3 and constitutive sera of ZIKV-reactive pools were tested individually. Donor sera were tested prospectively and retrospectively. A posttransfusion follow-up of a patient transfused with ZIKV RNA-reactive blood products was implemented. RESULTS: NAT detected 42 blood donor sera as ZIKV RNA reactive of 1505 tested (2.8%). Thirty ZIKV RNA-reactive blood products collected before the implementation of NAT were transfused to 26 recipients. Posttransfusion investigations were conducted by the hemovigilance unit and data were available for 12 recipients. Symptomatic ZIKV-TT infections were not reported. CONCLUSION: Predonation screening of blood donors, postdonation information, products discard, and quarantine of blood products were not effective enough to prevent transfusion of ZIKV RNA-reactive blood products. ZIKV NAT was an effective measure once implemented to prevent transfusion of ZIKV RNA-reactive blood products but it is difficult to evaluate the effectiveness of this measure to prevent ZIKV-TT infection, which is a rare event.

Pathogen inactivation of Dengue virus in red blood cells using amustaline and glutathione.

BACKGROUND: Dengue virus (DENV) is an arbovirus primarily transmitted through mosquito bite; however, DENV transfusion-transmitted infections (TTIs) have been reported and asymptomatic DENV RNA-positive blood donors have been identified in endemic countries. DENV is considered a high-risk pathogen for blood safety. One of the mitigation strategies to prevent arbovirus TTIs is pathogen inactivation. In this study we demonstrate that the amustaline and glutathione (S-303/GSH) treatment previously found effective against Zika virus in red blood cells (RBCs) is also effective in inactivating DENV. STUDY DESIGN AND METHODS: Red blood cells were spiked with high levels of DENV. Viral RNA loads and infectious titers were measured in the untreated control and before and after pathogen inactivation treatment of RBC samples. DENV infectivity was also assessed over five successive cell culture passages to detect any potential residual replicative virus. RESULTS: The mean ± SD DENV titer in RBCs before inactivation was 6.61 ± 0.19 log 50% tissue culture infectious dose (TCID50 )/mL and the mean viral RNA load was 8.42 log genome equivalents/mL. No replicative DENV was detected either immediately after completion of treatment using S-303/GSH or after cell culture passages. CONCLUSION: Treatment using S-303/GSH inactivated high levels of DENV in RBCs to the limit of detection. In combination with previous studies showing the effective inactivation of DENV in plasma and platelets using the licensed amotosalen/UVA system, this study demonstrates that high levels of DENV can be inactivated in all blood components.

Inactivation of Zika virus in platelet components using amotosalen and ultraviolet A illumination.

BACKGROUND: Concerned over the risk of Zika virus (ZIKV) transfusion transmission, public health agencies recommended the implementation of mitigation strategies for its prevention. Those strategies included the use of pathogen inactivation for the treatment of plasma and platelets. The efficacy of amotosalen/ultraviolet A to inactivate ZIKV in plasma had been previously demonstrated, and the efficacy of inactivation in platelets with the same technology was assumed. These studies quantify ZIKV inactivation in platelet components using amotosalen/ultraviolet A. STUDY DESIGN AND METHODS: Platelet components were spiked with ZIKV, and ZIKV infectious titers and RNA loads were measured by cell culture-based assays and real-time polymerase chain reaction in spiked platelet components before and after photochemical treatment using amotosalen/ultraviolet A. RESULTS: The mean ZIKV infectivity titers and RNA loads in platelet components before inactivation were either 4.9 log10 plaque forming units per milliliter, or 4.4 log10 50% tissue culture infective dose per milliliter and 7.5 log10 genome equivalents per milliliter, respectively. No infectivity was detected immediately after amotosalen/ultraviolet A treatment. No replicative virus remained after treatment, as demonstrated by multiple passages on Vero cell cultures; and ZIKV RNA was not detected from the first passage after inactivation. Additional experiments in this study demonstrated efficient inactivation to the limit of detection in platelets manufactured in 65% platelet additive solution, 35% plasma, or 100% plasma. CONCLUSION: As previously demonstrated for plasma, robust levels of ZIKV inactivation were achieved in platelet components. With inactivation of higher levels of ZIKV than those reported in asymptomatic, RNA-reactive blood donors, the pathogen-inactivation system using amotosalen/ultraviolet A offers the potential to mitigate the risk of ZIKV transmission by plasma and platelet transfusion.

Inactivation and removal of Zika virus during manufacture of plasma-derived medicinal products.

BACKGROUND: Zika virus (ZIKV) is an emerging mosquito-borne Flavivirus of major public health concern. The potential for ZIKV transmission by blood transfusion has been demonstrated; however, inactivation or removal of ZIKV during the manufacture of plasma-derived medicinal products has not been specifically investigated. STUDY DESIGN AND METHODS: Inactivation of ZIKV by pasteurization and solvent/detergent (S/D) treatment was investigated by spiking high-titer ZIKV stocks into human serum albumin and applying either heat or adding different mixtures of S/D reagents and assaying for infectious virus particles. Removal of ZIKV was evaluated using filters of differing pore sizes (75, 40, 35, and 19 nm), assaying for infectious virus and RNA. Electron microscopy was performed to determine the size of ZIKV particles. Neutralization of virus infectivity by immunoglobulins was investigated. RESULTS: ZIKV was effectively and rapidly inactivated by liquid heat treatment as well as by various mixtures of S/D reagents with reduction factors more than 4 log, in each case. Effective reduction of ZIKV infectivity was demonstrated for virus filtration for filters with average pore sizes of not more than 40 nm, although a significant proportion of virus RNA was detected in the 40- to 35-nm filtrates likely due to the presence of subviral particles observed by electron microscopy. None of the immunoglobulin preparations investigated neutralized ZIKV infectivity. CONCLUSIONS: Pasteurization and S/D treatment very rapidly inactivated ZIKV and filters with a pore size of not more than 40 nm removed all infectious ZIKV, demonstrating the effectiveness of these virus reduction strategies used during the manufacture of plasma-derived medicinal products.