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Table of Contents
Year : 2021  |  Volume : 58  |  Issue : 3  |  Page : 228-231

Severity of dengue illness and presence of anti DV IgG in serum of laboratory confirmed dengue cases

Department of Microbiology, King George’s Medical University, Lucknow, India

Date of Submission21-Jul-2019
Date of Decision25-Jun-2020
Date of Web Publication15-Feb-2022

Correspondence Address:
Prof. Amita Jain
Department of Microbiology, King George’s Medical University, Lucknow 226003
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-9062.325637

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Background & objectives: Presence of dengue is reported from India since 1960s. Secondary dengue infection may be more severe than primary, hence, distinction between primary and secondary dengue is essential. A way to detect secondary dengue is demonstration of anti DV IgG in patients’ serum. In this study we explored the association of dengue severity with anti DV IgG positivity.
Methods: Laboratory confirmed cases of dengue (positive for anti DV IgM/ NS-1 Antigen/ DV –RNA), presenting to the hospital within 7 days of illness, were consecutively enrolled for a period of one month (September 1–30, 2018) and were tested for anti DV IgG in their serum. All PCR positive samples were serotyped. Cases positive for anti-dengue IgG were labeled as secondary cases. Clinical details were collected to assess the severity of illness. Association of dengue severity with anti DV IgG positivity was calculated.
Results: Of the 128 dengue positive cases, 89 (69.5%) were anti DV IgM positive, 72 (56.3%) were Dengue NS-1 positives and 37 (28.9%) were DV-RNA positive. Only 39 (30.5%) cases were having detectable anti-dengue IgG in their serum (secondary dengue). Anti-dengue IgM positivity was significantly higher in secondary dengue cases. No association of anti DV IgG positivity was seen with severity of dengue illness.
Interpretation & conclusion: No association of IgG positivity with severity of illness was seen. D4 serotype is first time reported from Uttar Pradesh, India

Keywords: Anti Dengue IgG, Dengue Severity, Dengue serotypes; Primary dengue; Secondary dengue; Dengue serotypes

How to cite this article:
Jain A, Khan DN, Prakash O, Shukla S, Prakash S, Verma AK. Severity of dengue illness and presence of anti DV IgG in serum of laboratory confirmed dengue cases. J Vector Borne Dis 2021;58:228-31

How to cite this URL:
Jain A, Khan DN, Prakash O, Shukla S, Prakash S, Verma AK. Severity of dengue illness and presence of anti DV IgG in serum of laboratory confirmed dengue cases. J Vector Borne Dis [serial online] 2021 [cited 2023 Mar 29];58:228-31. Available from: http://www.jvbd.org//text.asp?2021/58/3/228/325637

  Introduction Top

Dengue fever (DF) is a serious illness caused by dengue viruses (DV) belonging to the family Flaviviridae, Genus Flavivirus. Dengue virus has 4 serotypes: 1, 2, 3, 4. Dengue is endemic in India since the 1960s and asymptomatic infections are more frequent than the symptomatic[1] infections. The World Health Organization (WHO) 2009 classification divides dengue as severe and non-severe dengue, with or without warning signs. Literature suggests that severe DENV infection like dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) are chiefly seen with secondary infection[2],[3]. Considering this, it becomes important to distinguish primary from secondary dengue early on in the course of illness. It helps in predicting prognosis and also in deciding; whether a patient needs admission and close monitoring or could be managed at home.

In practice, presence of anti DV IgG in patient’s sera is considered indicative of secondary dengue, more so if patient is reporting within 7 days of illness, meaning that presence of anti DV IgG in patient’s sera suggests high probability of severe disease. However, there are no guidelines, which suggest that patient positive for anti DV IgG should be kept under observation for development of any severe manifestations. In the present study, we are studying the association of severity of illness with presence of anti DV IgG in laboratory confirmed cases of dengue.

  Material & Methods Top

Study design

Over a period of 1 month, during September 1–30, 2018, total dengue laboratory confirmed cases (serum tested positive for anti-dengue IgM and/ or NS-1 antigen and/or Dengue RNA real time PCR), were consecutively enrolled.

Study type

Experimental study

Case definition of suspected dengue as per WHO criteria

Fever and two of the following criteria:

  • Nausea, vomiting
  • Rash
  • Aches and pains
  • Tourniquet test positive
  • Leukopenia
  • Any warning sign: (Abdominal pain or tenderness / Persistent vomiting /Clinical fluid accumulation/ Mucosal bleed/ Lethargy, restlessness /Liver enlargement >2 cm/ Laboratory: increase in HCT concurrent with rapid decrease in platelet count

Inclusion criteria

All dengue suspected cases confirmed by laboratory

Dengue serology/molecular tests.

Age group 0–80yrs

Exclusion criteria

Coinfected with other IgM antibodies like Chikungunya and/or Japanese encephalitis and/ or scrub typhus.

Laboratory diagnosis

The detection of NS1 antigen was done using Panbio Dengue Early ELISA kit (Standard Diagnostic Inc. Republic of Korea) as per manufacturer’s instructions. The detection of IgM antibodies was done using Dengue- IgM capture ELISA kit (MAC ELISA kit developed by the National Institute of Virology, Pune, India) as per the manufacturer’s instructions. Anti-dengue IgG were detected by ELISA kit (Panbio Dengue IgG Capture ELISA by Standard Diagnostic Inc. Republic of Korea) as per manufacturer’s instruction. The Panbio Dengue IgG Capture ELISA determines the elevated level of IgG antibodies to dengue virus in a patient’s serum with secondary dengue infection. A positive result [>22 Panbio Units] is indicative of active secondary infection). Dengue RNA in serum was detected by previously reported method by real time PCR[4].

Serum of DV positive cases was tested for anti DV IgG. Those which were positive for anti DV IgG were labeled as secondary cases and those which tested negative were labeled as primary case.

All PCR positive samples were processed for serotyping of dengue virus by method of Lanciotti et al[5].

Following clinical details of the patients were collected: age/ sex, day of illness on hospital reporting (less or more than 7 days), severe myalgia and back pain, retro-orbital pain, rash, oedema, neurological manifestations, bleeding from any site and need for hospitalization. Patients/ families were followed up after Day 15 to record the outcome (recovered or not).

Group differences were compared using Fisher’s exact test two sided for categorical variables and the Chi Square test for trend for continuous variables (age). P-values of 0.05 or less were considered statistically significant.

Ethical statement

All the cases provided consent and study was approved by Institutional ethics committee (83ECM IIA/ P9).

  Results Top

Of the total 128 dengue positive cases, 89 (69.5%) cases were anti DV IgM positive, 72 (56.3%) were Dengue NS-1 positives and 37 (28.9%) were DV-RNA PCR positive [Table 1]. Only 39 (30.5%) cases were having detectable anti dengue IgG in their serum (secondary dengue), while 89 (69.5%) cases were negative for anti-dengue IgG (primary dengue). Most of the patients were reporting to the hospital before 7 days of illness (76.6%), in spite of that anti dengue IgG positivity was only 30.5%. [Table 1] analyses the significance of difference in different clinical and diagnostic factors in primary and secondary dengue. Anti-dengue IgM positivity was significantly higher in secondary dengue cases while NS-1 and PCR positivity was higher in primary dengue cases. No other clinical parameters were significantly associated with either primary or secondary dengue. All the patients who were hospitalized were discharged from hospital after recovery. None of the patients died and none had any residual damage.
Table 1: Primary and Secondary dengue Infection

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All the PCR positive samples were subjected to serotyping, of which, dengue strains from 4/8 of secondary and 25/29 primary dengue cases could be serotyped [Table 2]. Rest could not be serotyped due to low viral load in the sample. DV serotypes 2 and 3 were most commonly circulating types. For the first time we are reporting DV serotype 4 from Uttar Pradesh, India. Co-infection of DV 1 and DV 2 was seen in 2 cases and of DV2 and DV 3 was seen in one case.
Table 2: Serotypes of dengue strains in primary and secondary dengue cases

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  Discussion Top

In the present study only 39 of 128 (30.5%) cases were secondary dengue. It is believed that higher number of secondary dengue infections is seen in dengue endemic countries. In spite of the fact, that dengue is endemic in Uttar Pradesh, India; most of the cases were of primary dengue. In our study majority of patient reported before 7 days of illness, although most of them were between 4–7 days. The possibilities of detection of IgG after 7 days of illness increases even in primary infection. In the present study in both primary and secondary dengue group around 3/4 cases were <7 days of illness.

Primary infection is usually considered benign and severity in dengue is linked to the antibody dependent enhancement, initiated by secondary infection with a different serotype[6]. In the present study around 1/4 patients needed hospitalization, but, all of them were discharged after successful management. No death was reported and severe clinical manifestations like bleeding and brain involvement were not frequent. We had a much higher percentage of males compared to the females (9:4). The male to female ratio in our hospital admissions generally remains 2:1; hence it is difficult to comment on male to female ratio specifically in this group of patients.

Serotype D3 was most commonly detected, followed by D2 and D1. We have seen the change in circulating serotypes from year to year[7]. It is for the first time we have detected D4 from UP, India, although D4 is reported from other states of India[8]. Three of the cases had co-infection with more than one serotypes. None of them needed hospitalization. The viral load in patients without anti DV IgG was higher in comparison to those with anti DV IgG, as viral strains from 25 of the 29 PCR positive IgG negative cases could be serotyped in contrast to 4 of the 8 PCR positive IgG positive cases of dengue. The severity of illness as manifested by need for hospitalization could not be linked to a specific dengue serotype.

One limitation of our study is the assumption, that presence of anti-dengue IgG is secondary infection. There are many limitations in differentiating primary from secondary dengue cases. IgG class of antibodies start appearing in the blood by Day 7 of illness even after primary dengue infection. Though 3/4 cases were less than 7 days of illness, we did not get enough cases before three days of illness to be sure of secondary dengue in presence of anti-dengue IgG. IgG avidity can be used to discriminate among primary dengue and secondary dengue infection[9], but, the IgG and IgM ELISA has the benefit of easier use. Several studies have been performed to discriminate primary and secondary DENV infection using the ratio of IgG and IgM at the different days of onset of symptoms[10],[11],[12],[13],[14]. The cut off for IgG/IgM ratio to differentiate primary and secondary DENV infection in our population is not described. Hemagglutination inhibition (HI) test is the standard reference test recommended by WHO to classify primary and secondary dengue virus infection[15]. This test requires paired serum samples, chemical pre-treatment to remove nonspecific inhibitors of hemagglutination, long time, and high technical skills and exhibits high cross-reactivity[16],[17].

  Conclusion Top

We found primary dengue to be more prevalent than secondary dengue in a dengue endemic area of Uttar Pradesh, India. There is circulation of all the four sero-types of dengue virus in Uttar Pradesh. Serotype D4 is being reported for the first time from this area. Severity of illness is not directly linked to presence of anti-dengue IgG in patient’s serum.

  Acknowledgements Top

We thank all our laboratory staff for their unconditional support.

Conflict of Interest: None

  References Top

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  [Table 1], [Table 2]


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