Clinical and virological characteristics of dengue in Surabaya, Indonesia

Abstract

Dengue disease is still a major health problem in Indonesia. Surabaya, the second largest city in the country, is endemic for dengue. We report here on dengue disease in Surabaya, investigating the clinical manifestations, the distribution of dengue virus (DENV) serotypes, and the relationships between clinical manifestations and the genetic characteristics of DENV. A total of 148 patients suspected of having dengue were recruited during February-August 2012. One hundred one (68%) of them were children, and 47 (32%) were adults. Dengue fever (DF) and Dengue hemorrhagic fever (DHF) were equally manifested in all of the patients. We performed DENV serotyping on all of the samples using real-time RT-PCR. Of 148, 79 (53%) samples were detected as DENV positive, with DENV-1 as the predominant serotype (73%), followed by DENV-2 (8%), DENV-4 (8%), and DENV-3 (6%), while 5% were mixed infections. Based on the Envelope gene sequences, we performed phylogenetic analyses of 24 isolates to genotype the DENV circulating in Surabaya in 2012, and the analysis revealed that DENV-1 consisted of Genotypes I and IV, DENV-2 was of the Cosmopolitan genotype, the DENV-3 viruses were of Genotype I, and DENV-4 was detected as Genotype II. We correlated the infecting DENV serotypes with clinical manifestations and laboratory parameters; however, no significant correlations were found. Amino acid analysis of Envelope protein did not find any unique mutations related to disease severity.

Fig 1. Dengue cases by monthly distribution (A), patients’ ages (B), and DENV serotype distribution (C) in Surabaya during 2012.

Fig 2. Maximum clade credibility (MCC) tree of DENV-1 genotype groupings generated by Bayesian inference method as implemented in BEAST using the GTR evolution model and gamma parameter rates from the E gene sequences.

The Surabaya 2012 isolates (red font) were grouped into Genotype I and Genotype IV based on classification by Goncalvez et al [27], together with isolates from Surabaya 2010 (green font) and other cities in Indonesia (blue font). The posterior probabilities of the clades are indicated as numbers in the node labels.

Fig 3. MCC tree of DENV-2 genotype groupings generated by Bayesian inference method as implemented in BEAST using the GTR evolution model and gamma parameter rates from the E gene sequences.

The Surabaya 2012 isolate (red font) was grouped into Cosmopolitan Genotypes based on classification by Twiddy et al [28], together with isolates from other cities in Indonesia (blue font). The posterior probabilities of the clades are indicated as numbers in the node labels.

Fig 4. MCC tree of DENV-3 genotype groupings generated by Bayesian inference method as implemented in BEAST using GTR evolution model and gamma parameter rates from the E gene sequences.

The Surabaya 2012 isolates (red font) were grouped into Genotype I based on classification by Lanciotti et al [29], together with isolates from Surabaya 2010 (green font) and other cities in Indonesia (blue font). The posterior probabilities of the clades are indicated as numbers in the node labels.

Fig 5. MCC tree of DENV-4 genotype groupings generated by Bayesian inference method as implemented in BEAST using GTR evolution model and gamma parameter rates from the E gene sequences.

The Surabaya 2012 isolate (red font) was grouped into Genotype II based on classification by Lanciotti et al [30], together with isolates from Surabaya 2010 (green font) and other cities in Indonesia (blue font). The posterior probabilities of the clades are indicated as numbers in the node labels.

Fig 6. Comparative analysis of amino acid substitutions within the Envelope protein among Surabaya DENV-1 viruses.

Only variable amino acids are shown.