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

Abstract

BackgroundChikungunya 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 FindingsThis 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/SignificancePublic 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.

Concomitant Transmission of Dengue, Chikungunya, and Zika Viruses in Brazil: Clinical and Epidemiological Findings From Surveillance for Acute Febrile Illness

“…Curiously, ZIKV spread in Salvador was very rapid and the outbreak, comprising ~17,500 case reports, lasted only two months [15,16], while the CHIKV emergence was less abrupt and lasted longer, hampering its prompt recognition, especially because public health attention was directed to the ZIKV outbreak [17]. Although our surveillance study included only one health unit of Salvador, our arboviral detection over time reflected previous citywide observations [15][16][17].…”

“…Particularly noteworthy was our finding of CHIKV circulation in Salvador at the same time (September 2014) that it was first detected causing outbreaks in other Brazilian cities [3,4], though apparently major amplification in Salvador only began in June 2015, one month after the ZIKV epidemic peak in May 2015 [15]. Curiously, ZIKV spread in Salvador was very rapid and the outbreak, comprising ~17,500 case reports, lasted only two months [15,16], while the CHIKV emergence was less abrupt and lasted longer, hampering its prompt recognition, especially because public health attention was directed to the ZIKV outbreak [17]. Although our surveillance study included only one health unit of Salvador, our arboviral detection over time reflected previous citywide observations [15][16][17].…”

Risk Factors for Chikungunya Outbreak in Kebridhar City, Somali Ethiopia, 2019. Unmatched Case-Control Study

“…To confirm this chikungunya outbreak Polymerase Chain Reaction (PCR) test was done and the positivity rate was 60%. Studies in other countries also showed that, the positivity rates of CHIKV among suspected cases ranges from 12.9% to 75% [13–16].…”

Emergence and persistence of the Chikungunya virus East-Central-South-African genotype in Northeast Brazil

“…To avoid misdiagnosis based on clinical symptoms only (2), viral RNA was extracted from 140 μL of serum samples using QIAmp viral RNA kit (Qiagen) and RT-qPCR analyses were performed for DENV serotypes 1-4 (3), ZIKV (4) and CHIKV (5). Two additional CHIKV RT-qPCR+ samples from Paraíba were included in subsequent analysis.…”