Laura B. Tauro

Coinfections of Zika and Chikungunya Viruses in Bahia, Brazil, Identified by Metagenomic Next-Generation Sequencing

ABSTRACT Metagenomic next-generation sequencing (mNGS) of samples from 15 patients with documented Zika virus (ZIKV) infection in Bahia, Brazil, from April 2015 to January 2016 identified coinfections with chikungunya virus (CHIKV) in 2 of 15 ZIKV-positive cases by PCR (13.3%). While generally nonspecific, the clinical presentation corresponding to these two CHIKV/ZIKV coinfections reflected infection by the virus present at a higher titer. Aside from CHIKV and ZIKV, coinfections of other viral pathogens were not detected. The mNGS approach is promising for differential diagnosis of acute febrile illness and identification of coinfections, although targeted arbovirus screening may be sufficient in the current ZIKV outbreak setting.

Distinct Zika Virus Lineage in Salvador, Bahia, Brazil.

Sequencing of isolates from patients in Bahia, Brazil, where most Zika virus cases in Brazil have been reported, resulted in 11 whole and partial Zika virus genomes. Phylogenetic analyses revealed a well-supported Bahia-specific Zika virus lineage, which indicates sustained Zika virus circulation in Salvador, Bahia’s capital city, since mid-2014.

Unrecognized Emergence of Chikungunya Virus during a Zika Virus Outbreak in Salvador, Brazil

Background Chikungunya virus (CHIKV) entered Brazil in 2014, causing a large outbreak in Feira de Santana, state of Bahia. Although cases have been recorded in Salvador, the capital of Bahia, located ~100 km of Feira de Santana, CHIKV transmission has not been perceived to occur epidemically, largely contrasting with the Zika virus (ZIKV) outbreak and ensuing complications reaching the city in 2015. Methodology/Principal Findings This study aimed to determine the intensity of CHIKV transmission in Salvador between November 2014 and April 2016. Results of all the CHIKV laboratory tests performed in the public sector were obtained and the frequency of positivity was analyzed by epidemiological week. Of the 2,736 tests analyzed, 456 (16.7%) were positive. An increasing in the positivity rate was observed, starting in January/2015, and peaking at 68% in August, shortly after the exanthematous illness outbreak attributed to ZIKV. Conclusions/Significance Public health authorities and health professionals did not immediately detect the increase in CHIKV cases, likely because all the attention was directed to the ZIKV outbreak and ensuing complications. It is important that regions in the world that harbor arbovirus vectors and did not experience intense ZIKV and CHIKV transmission be prepared for the potential co-emergence of these two viruses.

Epizootic Outbreak of Yellow Fever Virus and Risk for Human Disease in Salvador, Brazil.

Background: Yellow fever virus (YFV) is an RNA virus maintained in an enzootic, sylvatic cycle involving nonhuman primates (NHPs) and sylvatic mosquito vectors primarily of the genus Haemagogus and Sabethes. Transmission occasionally spills over to humans entering forested regions. In the Americas, urban transmission of YFV to humans has not occurred since the mid-1900s because of vaccination and near-elimination of the anthropophilic Aedes aegypti, the urban vector (1). However, concerns about reemergence of urban YFV have recently increased because of the reappearance and rapid spread of A aegypti in the urban environment. Furthermore, immunization coverage for YFV is insufficient because vaccination is generally indicated only for higher-risk populations, such as those living in or travelling to areas with sylvatic transmission. Objective: To investigate the 2017 epizootic outbreak of YFV and the risk for human disease in Salvador, Brazil. Methods and Findings: Since November 2016, deaths of NHPs due to YFV in Brazil have been reported in the state of So Paulo. Beginning in December 2016, human cases were also reported in the states of So Paulo and Minas Gerais. By the end of May 2017, the YFV outbreak in humans had spread to 9 Brazilian states, with more than 130 municipalities reporting confirmed cases (Appendix Figure 1), all deemed of sylvatic origin (rather than via urban A aegypti transmission). Of 3240 suspected reported human cases, 792 were laboratory-confirmed. Among all reported patients, 435 died and 274 of these had laboratory-confirmed infection with YFV (casefatality ratio for laboratory-confirmed cases, 34.6%) (2). Appendix Figure 1. Brazilian states where human cases of YFV were reported between December 2016 and May 2017, according to laboratory confirmation status. YFV = yellow fever virus. Reports of deaths of NHPs due to YFV also simultaneously increased. By the end of May 2017, a total of 3850 NHPs was suspected to have died of YFV infection, 642 of which were confirmed from 12 states (2). Since the beginning of the outbreak, the Brazilian Ministry of Health has distributed more than 25 million YFV vaccine doses to persons in areas with confirmed human or NHP cases, likely reducing incidence (2). On 14 January 2017, deaths of NHPs suspected of having YFV were first reported in Salvador, the fourth largest Brazilian city, which had not been considered a risk area for transmission (Appendix Figure 1). The number of NHPs found dead throughout the city rapidly increased, and by 24 August, 205 NHPs of the genus Callithrix suspected of having infection with YFV had been collected (Appendix Figure 2). Reverse transcriptase polymerase chain reaction testing for the virus was done on tissue samples of 21 dead animals at the Oswaldo Cruz Foundation in Rio de Janeiro; samples from 13 animals (61.9%) tested positive. Animals suspected of being infected were found throughout Salvador, with a cluster (3 of the 13 YFV-positive animals) around a city park, a 0.66-km2 recreational area of residual Atlantic forest with trees less than 10 m high (Figure). Appendix Figure 2. Temporal distribution of NHPs collected in Salvador, Brazil, by epidemiologic week in 2017. NHP = nonhuman primate. Figure. Spatial distribution of locations of NHP collections according to YFV status and of sites of mosquito collections in Salvador, Brazil. Distribution of 7 of the 8 YFV-negative NHPs, all 13 of the YFV-positive NHPs, and 173 of the 184 NHPs that were not tested is shown. NHP = nonhuman primate; YFV = yellow fever virus. To investigate potential vectors involved in YFV transmission among NHPs in Salvador, we initiated ground-level mosquito collections within and around the city park and the naval base, another preserved Atlantic forest area where dead, YFV-positive NHPs were found. During 10 days of fieldwork in 26 sites between 10 April and 7 June 2017, a total of 435 adult mosquitoes (307 females) was captured using human landing catches (Table). Most females captured were Wyeomyia species and A albopictus. Although we did not capture Haemagogus or Sabethes species, Haemagogus mosquitoes were identified in Salvador in January 2017 in a suburban, forested area. Pools of captured female mosquitoes from each species were tested for YFV by reverse transcriptase polymerase chain reaction (primers CAG and YF7) (3) and cell culture (C6/36, A albopictus), and none was positive. Table. Number of Mosquitos Collected at Ground Level in Salvador, Brazil* Discussion: To date, urban Aedes mosquitoes have not been associated with YFV transmission to humans in Brazil. However, cases of YFV in NHPs in densely urbanized areas pose a considerable risk for resurgence of A aegyptimediated YFV transmission to humans. Salvador has long been an epicenter of dengue transmission and more recently of Zika (4) and chikungunya (5) viruses, all with A aegypti as the main vector. In addition, A albopictus, which is susceptible to YFV infection in laboratory settings, is commonly found here, particularly in peridomestic and green areas. Although never implicated in natural YFV transmission, this species was only introduced into the Americas in the 1980s. Continuous entomologic and veterinary surveillance of mosquitoes and NHP deaths, accompanied by laboratory testing for YFV, is the cornerstone of assessing the risk that this virus will establish an urban transmission cycle. In parallel, scaling up YFV vaccination coverage is critical to prevent additional human cases of this disease.

Lack of evidence for Zika virus transmission by Culex mosquitoes

Emerging Microbes & Infections (2017) 6, e90; doi:10.1038/emi.2017.85; published online 18 October 2017

Does immunity after Zika virus infection cross-protect against dengue?

Brazilian National Council for Scientific and Technological Development (grant 550160/2010-8 to MGR, grants 400830/2013-2 and 440891/2016-7

Diagnostic performance of commercial IgM and IgG enzyme-linked immunoassays (ELISAs) for diagnosis of Zika virus infection

BackgroundSerologic detection of Zika virus (ZIKV) infections is challenging because of antigenic similarities among flaviviruses.ObjectiveTo evaluate the sensitivity and specificity of commercial ZIKV IgM and IgG enzyme-linked immunoassay (ELISA) kits.MethodsWe used sera from febrile patients with RT-PCR-confirmed ZIKV infection to determine sensitivity and sera from RT-PCR-confirmed dengue cases and blood donors, both of which were collected before ZIKV epidemics in Brazil (2009–2011 and 2013, respectively) to determine specificity.ResultsThe ZIKV IgM-ELISA positivity among RT-PCR ZIKV confirmed cases was 0.0% (0/14) and 12.5% (1/8) for acute- and convalescent-phase sera, respectively, while its specificity was 100.0% (58/58) and 98.3% (58/59) for acute- and convalescent-phase sera of dengue patients, and 100.0% (23/23) for blood donors. The ZIKV IgG-ELISA sensitivity was 100.0% (6/6) on convalescent-phase sera from RT-PCR confirmed ZIKV patients, while its specificity was 27.3% (15/55) on convalescent-phase sera from dengue patients and 45.0% (9/20) on blood donors’ sera. The ZIKV IgG-ELISA specificity among dengue confirmed cases was much greater among patients with primary dengue (92.3%; 12/13), compared to secondary dengue (7.1%; 3/42).ConclusionsIn a setting of endemic dengue transmission, the ZIKV IgM-ELISA had high specificity, but poor sensitivity. In contrast, the ZIKV IgG-ELISA showed low specificity, particularly for patients previously exposed to dengue infections. This suggests that this ZIKV IgM-ELISA is not useful in confirming a diagnosis of ZIKV infection in suspected patients, whereas the IgG-ELISA is more suitable for ZIKV diagnosis among travelers, who reside in areas free of flavivirus transmission, rather than for serosurveys in dengue-endemic areas.

Can Zika virus antibodies cross-protect against dengue virus? – Authors' reply

Fil: Ribeiro, Guilherme S.. Fundacion Oswaldo Cruz; Brasil. Universidade Federal da Bahia; Brasil

Discovery of a persistent Zika virus lineage in Bahia, Brazil

Metagenomic next-generation sequencing coupled with capture probe enrichment was used to recover 11 whole and partial Zika virus (ZIKV) genomes from patients in Bahia, Brazil from April 2015 to January 2016, where the majority of suspected Brazilian ZIKV cases have been reported. Phylogenetic reconstructions and molecular clock analyses using the newly generated data uncovered the existence of a Bahia-specific ZIKV lineage sharing a common ancestor in mid-2014, indicating sustained circulation of this strain in Bahia since that date.