Dengue COVID-19 overlap: antigenic mimicry or concurrent two viral diseases

: Background : Dengue-COVID-19 overlap is mixture of both diseases sharing few similarities in pulmonary and extrapulmonary involvement. Due to high prevalence of both diseases later being pandemic disease, and overlapping laboratory and clinical parameters we have conducted a study to observe dengue-COVID-19 overlap in Indian settings in tertiary care hospitals. Methods-Prospective, observational study, included 600 COVID-19 cases with dengue NS1 or Dengue IgM positive, with lung involvement documented and categorized on HRCT thorax at entry point. All cases were subjected to dengue IgG antibody titers and dengue IgM/IgG antibody titer analysis after 12 weeks of discharge form hospital. Results: Dengue-COVID-19 overlap was documented in 16.33% (98/600) cases. CT severity has documented significant correlation with Dengue-COVID-19 overlap cases. [p<0.00001] Hematological evaluation, white blood cell count & platelet count were having significant association with Dengue-COVID-19 overlap [p<0.0076] & [p<0.00001] respectively. Clinical parameters as hypoxia have significant association with dengue-COVID-19 overlap. [p<0.00001] Inflammatory markers as IL-6, CRP and LDH has significant association in dengue-COVID-19overlap [p<0.00001] respectively. In study of 98 cases of ‘Dengue-COVID-19’, post covid lung fibrosis [p<0.004] and serological assessment in dengue IgM/IgG and covid antibody titers has significant association [p<0.00001] Conclusion: Dengue-COVID-19 overlap is clinical syndrome with overlapping clinical and laboratory workup of both the illnesses. High index of suspicion is must in all covid cases in tropical settings where dengue is endemic; and all cases with leucopenia and thrombocytopenia with fever should be screened for dengue serology. False positive dengue serology or dengue antigen cross-reactivity is known to occur in underlying COVID-19 illness, and have impact on clinical outcome as it will result in delay in covid appropriate treatment initiation and many cases require intensive care unit treatment due to progressed covid pneumonia.


Introduction:
Corona virus related global pandemic (COVID- 19), declared by World Health Organization (WHO) in March 2020, caused by novel Coronavirus SARS-CoV-2 resulted in significant mortality morbidity, with impact on health care systems globally resulting shortage of resources to manage rapidly growing pandemic. 1Dengue fever is arboviral vector born disease with four antigenic variants, and as per WHO figures, dengue has shown significant increase in disease burden in all parts of world causing 100-400 million infections each year with more than 50 percent in tropical settings. 2Asian countries are significantly affected by COVID-19 and Dengue both, due to favorable geographical trends in tropical settings concurrent occurrence is more possible along with predicted antigenic cross reactivity and resurgence of both disease is expected in future. 3,4,5COVID-19 and dengue, both are viral disease sharing clinical and laboratory similarities and increase in chances of underestimation resulting in delay in diagnosis if proper laboratory workup and specific diagnostic tests are not performed. 6Antigenic cross-reactivity resulted in false positive results, and will manifest significantly in patient view and public health due to increased disease burden and poor outcomes due to delay in diagnosis and treatment. 7,8VID-19 pandemic is a big health concern in dengue endemic areas due to overlapping of clinical and laboratory features and its challenging job for critical care physicians for correct diagnosis and management of both the diseases. 9,10,11Many case reports and case series published the concurrent COVID-19 and dengue co-infections 12,13 , which has been associated more mortality than isolated single infection. 14,15Both are RNA viruses and shown similar pathologic pathways as cytokines and chemokine release, altering the integrity of the vascular endothelium leading to vasculopathy, coagulopathy and capillary leak. 16 present study, we have documented COVID-19 pneumonia cases with concurrent dengue like manifestations and dengue serology positivity i.e., either NS1 or IgM antibody positive; and we have followed these cases for 12 weeks to exactly confirm dengue-covid overlap.

Data source:
Prospective, observational study conducted in Venkatesh chest hospital, and Pulmonary Medicine, MIMSR medical college Latur during May 2021 to March 2022, to find out 'COVID-Dengue Overlap' in diagnosed COVID-19 pneumonia cases admitted in critical care unit.Total 600 cases were enrolled in study after IRB approval and written informed consent of patient.
Inclusion criteria: COVID-19 patients, confirmed with RT-PCR, above the age of 18 years, hospitalized in the study centers, including those with comorbidities and irrespective of severity and oxygen saturation were included in the study.

Exclusion criteria:
Those not willing to give consent, not able to perform follow-up dengue and COVID-19 antibody titers, and cases that died during hospitalization or before 12 weeks of discharge from hospital and patients less than 18 years of age were excluded.

Statistical Analysis:
The statistical analysis was done using chi test in R-3.4 software.Significant values of χ2 were seen from probability table for different degree of freedom required.P value was considered significant if it was below 0.05 and highly significant in case if it was less than 0.001

Results:
Covariates: [    17,18 Presently, majority of the Asian countries are badly affected with COVID-19 pandemic and resulted in socioeconomic crisis due significant disease burden in compromised health sector. 19,20,21,22,23India is one of the most affected country due to COVID-19 with ranked second and third in number of affected cumulative cases and deaths respectively. 24Now, most of the South East Asia region has documented full blown COVID-19 pandemic with more cases and deaths in comparison to rest of world. 25,26,27 present study, we have observed many cases were initiated treatment in consideration of dengue fever due to overlap of common symptom of fever and later on during course of illness when these patients started cough and or shortness of breath, were evaluated for COVID-19 and documented positive serology with lung parenchymal involvement on HRCT thorax.Authors, Tsheten T et al 28 , Chen N et 9 & Afrin, S. F et al 14 documented similar findings.
We have also observed that clinical worsening or requirement of oxygen supplementation due to fall in oxygen saturation was reason to investigate for underlying COVID-19 in primary dengue hospitalizations, and vice versa.Authors, Estofolete CF et al. 15 , Mahajan NN et al. 29 , Bicudo N et al. 30 & Rodriguez-Morales AJ et al. 31 Numerous authors Tsheten T et al 28 , Pontes RL et 32 and Ratnarathon AC et al 33 documented similar observation.As both diseases share same pathophysiologic mechanism, hematological manifestations as thrombocytopenia resulted from decreased production due to bone marrow suppression or increase immune mediated consumption 34,35 or immune complex mediated and autoantibody dependent platelet destruction which has been documented in COVID-19 and dengue both. 35,36

'Dengue-COVID-19 overlap': Is it an 'antigenic mimicry'?
In  51 , and factors associated with persistence of virus for longer duration is area of research. 45In COVID-19 serology, IgM antibody increase during first week with peak at around 2 week of illness and then disappear over two to four weeks, while IgG antibody start rising by the end of first week and remains elevated and detectable level till 90 days of infection.Still, exactly protective value of these antibodies in preventing reinfections is not clearly known. 46afat N et al 47 observed that in Primary Acute Dengue infection, NS1 and viral RNA has been documented in first week of illness till first 5 days of infection, serology as IgM antibody documented at 3-5 days and remains detectable for several weeks to months, and at the end of acute phase, IgG antibody start rising which last for 10 days which establishes immunological memory for several years.While in secondary dengue infection, IgG antibody rises earlier than IgM. 47Recent studies 52,53,54 have documented role of neutralizing antibodies in these infections which will disappear after 3 months.Long et al 52 observed short lasting serological stage and early waning of humoral immunity with 40% percent asymptomatic individuals became seronegative and 12.9% of the symptomatic cases became negative for IgG in the early convalescent phase.Wu F et al 54 mentioned the doubtful role of these neutralizing antibodies in protection from future infections due to various variants, and really how much they protect us from reinfection is not known at present.
We have further analyzed these 14 cases, and documented that all these 14 cases were having mild lung involvement on CT thorax imaging, which means that more immunopathological nature of corona virus disease leading to short lasting humoral immunity and ultimately 'short lasting immune memory' or 'viral escape from immune restoration phenomenon' by altering and targeting 'immune escape pathway' which will hide the COVID-19 antigen presentation and sensing to memory T cells of host and developing protective antibodies for same.

Other important observations in present study:
Hematological parameters were having significant association in COVID-19 cases with and without dengue overlap, especially normal and abnormal white blood cell count [p<0.0076] and normal or abnormal platelet count [p<0.00001]Rational for similar observations were more immunological nature of Dengue-COVID-19 overlap' syndrome.
Clinical parameters like oxygen saturation at entry point i.e. with or without hypoxia have significant association in COVID-19 cases with and without dengue overlap.[p<0.00001]Rational for similar observation in Dengue-covid overlap as compared to isolated covid illness, where lung involvement was predominant pathological nature of covid and hypoxia was predominantly documented in these cases due to more pulmonary involvement. 48flammatory markers analysis such as IL-6 [p<0.00001],CRP [p<0.00001] and LDH [p<0.00001] has documented significant association in COVID-19 cases with and without dengue overlap.[p<0.00001]Rational for same findings were more immune nature of overlap cases as compared to isolated covid cases, and predominant pattern of involvement is pulmonary, leading to direct pulmonary alveolar and vascular involvement and correlated with raised inflammatory markers IL-6, CRP and LDH.We used LDH as marker of assessment of oxygen status and hypoxia, and observed grossly raised it with predominant lung involvement as documented in previous study.4. How much dengue will impact in ongoing COVID-19 pandemic in spite of increase in cost of care of both the illnesses with fatigued manpower and health system? or we should prepare for both the disease as top priority in incoming few years with rising trends of various variants of corona virus?Time will decide, but as of now Lancet Commission [39] also warrants covid-dengue as a hot topic of medical research and disease of concern for medical experts across the globe due to shared common pathophysiological and biological pathways.
5. Timely workup will save economic expenses in this ongoing pandemic which has resulted into disastrous effects on global economy and unemployment.Author Huda, N et al [55] & Ibrahim, M. S et al [56] documented similar observation and mentioned positive effects in facing economic challenges during this COVID-19 pandemic.

Conclusions:
Dengue-COVID-19 overlap is clinical syndrome with overlapping clinical and laboratory workup of both the illnesses.High index of suspicion is must in all covid cases in tropical settings where dengue is endemic; and all cases with leukopenia and thrombocytopenia with fever should be screened for dengue serology.False positive dengue serology or dengue antigen cross-reactivity is known to occur in underlying COVID-19 illness, and have impact on clinical outcome as it will result in delay in covid appropriate treatment initiation and many cases require intensive care unit treatment due to progressed covid pneumonia.
Covid-19 and Dengue antigenic cross-reactivity has significant association with lung fibrosis as a resultant pathophysiological effect of the immune activation pathway; and these cases required longer oxygen supplementation and anti-fibrotics in follow up.'Dengue-COVID-19 overlap' is very frequently documented in tropical settings and disease of concern in critical care settings; as the natural trend of this entity is different and has an impact on clinical outcome if diagnosis is delayed.Both diseases may behave like 'two sides of the same coin', and rational for coexistent pathology were still undetermined.

design: All study cases were undergone following assessment before enrolling in study:
This study is approved by the Institutional Review Board/ Ethics Committee of MIMSR Medical college, Venkatesh chest Hospital and Critical Care Center Latur India (approval # VCC/109-2021-2022; approval date 31/05/2021).COVID-19 RT PCR test performed in all cases, if first test results were negative and radiological features clearly documenting pneumonia, we have repeated RT PCR test and enrolled all cases with positive COVID-19 RT-PCR test.HRCT Thorax to

'Dengue-COVID-19 overlap': Is it a coexistent two different viral genotypic disease?
40,42ng in tropical countries in South East Asia region and as pandemic grown across globe irrespective of Dengue trends, now it is considered as global health issue.Various studies41,42and author Epelboin L et al13, Saavedra-Velasco M et al.40documented similar observation.'Covid-