Discussion and Conclusions
Physicians should be aware of the possibility of dengue and COVID-19 coinfection in areas with overlapping outbreaks and be aware of a potentially harmful interaction between these viruses. In the acute phases of both infections, symptoms are similar and overlap, which may delay appropriate diagnosis and treatment. Details of the comparison between COVID-19 and dengue infection are presented in Table 2. This can have serious clinical consequences, either through failure of adequate hydration or delay in the use of anticoagulants, corticosteroids, and early mechanical ventilation.[9,10]
It is important to keep in mind the clinical and epidemiological particularities of each virus in coinfection to better guide the diagnosis and prognosis. Thus, for example, dengue fever frequently has serious manifestations in young adults because most are experiencing the effects of a second infection, whereas COVID-19 is generally asymptomatic or has few symptoms in this population, as was observed in case 1. In the elderly, dengue severity depends mainly on the presence of comorbidities or the infectious serotype. However, COVID-19 is consistently more severe in older age groups, especially in patients with decompensated comorbidities, as was observed in the second case.[11,12]
In these cases, laboratory tests are very useful because, in addition to determining whether the agent is present in the body, tests help to discern the disease's phase. However, it is important to consider tests' limitations. Recently, the possible alteration of dengue serological test results during the COVID-19 pandemic has been reported. Yan et al. described the case of two patients in whom SARS CoV-2 infection was confirmed by rRT-PCR, but in addition IgM/IgG serology was positive for dengue. However, RT-PCR for dengue was negative. Given the time of symptoms, the clinicians considered the dengue test to be a false-positive result.
According to this information, it is important to consider that, in primary dengue infection, both nonstructural protein 1 (NS1) and viral RNA can be detected from the onset of symptoms until approximately day 5 of infection. The immune response usually appears at two times. During the acute phase, immunoglobulin M (IgM) appears on approximately the third to fifth day of infection and may remain at detectable levels for several months. Immunoglobulin G (IgG) rises towards the end of the acute period, which lasts an average of 10 days and confers immunological memory for the infecting serotype, which can persist for years. IgG does not usually appear during the acute phase of primary disease. However, in secondary infection, IgG rises even earlier than IgM.
In SARS-CoV-2, the viral load in respiratory specimens is highest during the initial phases of the disease, reaching a peak during the second week of infection. It then decreases until it becomes undetectable in most cases. In severe disease, the viral load in respiratory fluids is highest at approximately the third and fourth weeks. The factors that cause the viral load to persist more in some individuals than in others remain to be clarified. Synthesis of antibodies against SARS-CoV-2 is a primary immune response to infection. IgM levels increase during the first week after infection, peaking after 2 weeks; they then tend to disappear in most individuals. IgG is detectable after the first week and remains elevated for approximately 90 days. However, it is not yet clear whether these antibodies can protect against reinfection during that time.
In summary, the negative result of the diagnostic tests, either in COVID-19 or dengue fever, does not rule out infections when the clinical symptoms are suggestive, especially in early stages. In patients with several days of symptoms, the probability of finding RT-PCR for dengue positivity is low, since the sensitivity of the test decreases further along the course of illness, as observed in the second case. It has been seen that RT-PCR tests for SARS CoV-2 can be positive for longer periods, which is an interesting difference compared with direct dengue tests.[16,17] Given the above, the possibility of having discordant results in the diagnostic tests during dengue/SARS CoV-2 coinfection raises the need to clarify the dynamics of the clinical evolution of both diseases and to take positive or negative laboratory test results with caution.[4,18]
In conclusion, dengue virus and SARS CoV-2 coinfection are possible, and should be suspected in dengue endemic areas. The diagnosis requires a combination of tools, tests for the direct detection of virus, and indirect tests that measure the immune response, in addition to an adequate interpretation of the results according to the clinical and epidemiological particularities of both infections.
WHO: World Health Organization; AST: Aspartate aminotransferase; ALT: Alanine aminotransferase; WBC: White blood cell; ICU: Intensive care unit.
This work was financed by the Fundacion Valle del Lili through resources from the institutional registry COVID-19-RECOVID.
Availability of data and materials
The datasets used during the current study are available from the corresponding author on reasonable request.
Ethics approval and consent to participate
This work was reviewed and approved by the Ethics Committee on Biomedical Research of the Fundacion Valle del Lili (IRB/EC No. 1566), following the precepts of the Declaration of Helsinki and Resolution 8430/1993 of the Colombian Ministry of Health.
Consent for publication
Written informed consent was obtained from the patient of case report 1 for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal. For patient 2, no informed consent was required because this study was conducted retrospectively based on information collected from an institutional case record of COVID-19 carried out at the Fundacion Valle del Lili (COVID-19-RECOVID).
J Med Case Reports. 2021;15(439) © 2021 BioMed Central, Ltd.