*2.4.2.2. IgG ELISA*

The IgG is detected with low titers when ending the first week of the onset symptoms in humans, and they could even be detected for a lifelong. The tests to detect an IgG using the virus bind to a plate in a smooth antigen way (protein cocktail) usually present a low specificity so that there is a cross-reaction with other viruses from the same genus due to the proteins found in the antigen, and this test cannot be used to determine the infectious dengue serotype but it can present a higher sensitivity than the hemagglutination inhibition test. The ELISA is also used for studying how different IgG sub-classes react in a dengue infection [5, 7–9].

#### *2.4.2.3. IgG inhibition ELISA tests*

It can be used to differentiate a primary infection and a secondary infection from dengue replacing an hemagglutination inhibition test using a percentage of inhibition higher or the same as 50% as a positivity criterion. In case of having only a serum sample, a primary infection is considered when the antibody IgG titer is ≤20, and a secondary infection is considered if the antibody titer is ≥1280. In both cases, the sample must be collected on 5–7 days. If there are paired samples, a primary infection is considered when the seroconversion in antibody titers from the acute and convalescent phase occurs, and a secondary infection is considered when the antibody titers increase four times or more between the acute and convalescent phase, or in both serums [6].

## *2.4.2.4. IgA ELISA test*

*2.4.1.10. Automated equipment for virus counting*

66 Dengue Fever - a Resilient Threat in the Face of Innovation

using the viral isolation as a reference test [28].

*2.4.1.11. Enzyme-linked immunosorbent assay (ELISA) for NS1*

factor depending on IgM ELISA type causes false positives [5, 7–9].

of fluorescent [27].

*2.4.2. Indirect methods*

*2.4.2.1. IgM ELISA*

*2.4.2.2. IgG ELISA*

*2.4.2.3. IgG inhibition ELISA tests*

There are redesigned flow cytometers to quantify a virus in solutions like The ViroCyt® Virus Counter (VC) 2100 (ViroCyt, Boulder, CO, USA) using a specific fluorescent dye for the envelope proteins and the other one for the nucleic acids that allows recognizing viral particles having both components in its structure. Then, it eliminates anything that represents one type

The NS1 nonstructural protein is produced during dengue infection and accumulated in higher concentrations in the human serum (up to 50 μg/ml) being detected during the acute phase (day 0–6) after the symptoms in primary and secondary infection start. Some studies have reported a correlation between elevated NS1 protein levels with hemorrhagic dengue cases, and even this technique seems to be effective to detect DENV in the vector. When evaluating three of these commercial tests from different manufacturers with human serum samples, it is found sensitivity between 85.5 and 95.9% and specificity between 95.0 and 100%

IgM can be detected on 50% infected people within 3–5 days and after the symptoms onset, and it reaches approximately to 80% infected people on day 5 and to 99% infected people on day 10 reaching maximum levels in humans at the 2 weeks to falter until they are not detected on 2–3 months. An indirect capture ELISA is usually used for detecting IgM, and it allows increasing sensitivity of the test in detecting antibodies. However, IgM antibodies are not specific, and they could present a cross-reaction with other flavivirus like YFV, ZIKV, etc. Besides, some particular test characteristics could alter the result of the test as the rheumatoid

The IgG is detected with low titers when ending the first week of the onset symptoms in humans, and they could even be detected for a lifelong. The tests to detect an IgG using the virus bind to a plate in a smooth antigen way (protein cocktail) usually present a low specificity so that there is a cross-reaction with other viruses from the same genus due to the proteins found in the antigen, and this test cannot be used to determine the infectious dengue serotype but it can present a higher sensitivity than the hemagglutination inhibition test. The ELISA is also used for studying how different IgG sub-classes react in a dengue infection [5, 7–9].

It can be used to differentiate a primary infection and a secondary infection from dengue replacing an hemagglutination inhibition test using a percentage of inhibition higher or the It was used in some studies to identify the infected people in an early stage of dengue infection. Thus, it was found 100% of sensitivity in people with secondary dengue infection after symptom onset-day 1. However, the results were not very favorable for primary infections [29].
