Investigation Into an Outbreak of Dengue-like Illness in Pernambuco, Brazil, Revealed a Cocirculation of Zika, Chikungunya, and Dengue Virus Type 1

Abstract

In April 2015, an outbreak of dengue-like illness occurred in Tuparetama, a small city in the northeast region of Brazil; this outbreak was characterized by its fast expansion. An investigation was initiated to identify the viral etiologies and advise the health authorities on implementing control measures to contain the outbreak. This is the first report of this outbreak in the northeast, even though a few cases were documented earlier in a neighboring city.Plasma samples were obtained from 77 suspected dengue patients attending the main hospital in the city. Laboratory assays, such as real-time reverse transcription polymerase chain reaction, virus cDNA sequencing, and enzyme-linked immunosorbent assay, were employed to identify the infecting virus and molecular phylogenetic analysis was performed to define the circulating viral genotypes.RNA of Zika virus (ZIKV) and Dengue virus (DENV) or IgM antibodies (Abs) to DENV or chikungunya (CHIKV) were detected in 40 of the 77 plasma samples (51.9%). DENV was found in 9 patients (11.7%), ZIKV was found in 31 patients (40.2%), CHIKV in 1 patient (1.3%), and coinfection of DENV and ZIKV was detected in 2 patients (2.6%). The phylogenetic analysis of 2 available partial DENV and 14 ZIKV sequences revealed the identities of genotype 1 and the Asiatic lineage, respectively.Consistent with recent reports from the same region, our results showed that the ongoing outbreak is caused by ZIKV, DENV, and CHIKV. This emphasizes the need for a routine and differential diagnosis of arboviruses in patients with dengue-like illness. Coordinated efforts are necessary to contain the outbreak. Continued surveillance will be important to assess the effectiveness of current and future prevention strategies.

FIGURE 1

Map of Brazil showing the geographical location of Tuparetama city (red colored) and Pernambuco State (red colored), where samples of the current outbreak were collected during May 25, 2015 to May 31, 2015.

FIGURE 2

Maximum-likelihood phylogenetic tree of the 2 established dengue virus genotype 1 (DENV-1) sequences identified in this study (indicated by red circles). The tree is based on 266-nt partial NS5 nucleotide sequences. The tree was generated by the ML method using the TN93 + G + I model implemented in the PHYML v.3.0 package. The approximate likelihood ratio test (aLRT) values of at least 70% are indicated at nodes. The tree was rooted with the Zika virus (GenBank: KJ776791) lineage from French Polynesia. The scale bar represents 0.05 nucleotide substitutions per site.

FIGURE 3

Phylogenetic tree constructed using a maximum-likelihood method from a partial NS5 region (689 bp; nt 8912–9601 of PLCal_ZV, GenBank: KF993678) of 14 samples from the present study (indicated by red circles), 51 sequences from Chile and 3 other Asiatic lineages (indicated by blue circle), and the 48 Zika virus sequences originated from Africa (indicated by green square). The tree was generated by the ML method using the TN93 + G + I model implemented in the PHYML v.3.0 package. The approximate likelihood ratio test (aLRT) values of at least 63% are indicated at nodes. The tree was rooted with the dengue virus (GenBank: KJ18936) genotype 1 from Puerto Rico.