Table 1.
Dengue case definitions
| Case | Definition |
|---|---|
| Suspected symptomatic dengue | Febrile illness with a body temperature ≥ 38°C (by any route) measured on two consecutive days, with or without the presence of other dengue symptoms and without an obvious reason to suspect a condition other than dengue (based on a physician’s judgment). |
| Laboratory diagnosis of suspected dengue cases | |
| Laboratory-confirmed dengue* | Positive DENV identification by serotype-specific quantitative real-time polymerase chain reaction on acute blood samples, or anti-DENV IgM seroconversion between acute and convalescent samples, or anti-DENV IgG “capture conversion”: negative IgG capture result on acute blood samples followed by a positive IgG capture result on convalescent blood samples. |
| Laboratory-probable dengue | Anti-DENV IgM or IgG positivity in at least 1 sample (acute or convalescent) and no evidence of viremia in acute samples and no evidence of anti-DENV IgM or IgG seroconversion between acute and convalescent samples. |
| Indeterminate dengue | Negative result for anti-DENV IgM and IgG antibodies in acute samples and no evidence of viremia in acute samples and convalescent samples not available. |
| Negative | Cases not eligible for the aforementioned categories, excluding “unknown” cases where no laboratory result was available, or the acute sample result was missing and the convalescent sample was negative. |
| Clinical severity of laboratory-confirmed symptomatic cases | |
| Laboratory-confirmed symptomatic dengue case, mild | Laboratory-confirmed dengue case with a body temperature ≥ 38°C measured on two successive days and no criterion for moderate to severe dengue. |
| Laboratory-confirmed symptomatic dengue case, moderate to severe | Laboratory-confirmed dengue case with at least one criterion: increased vascular permeability documented by objective evidence, such as hemoconcentration ≥ 20% or the accumulation of a pleural effusion (documented by right lateral decubitus chest X-ray or ultrasound on the day of defervescence or no later than one day after defervescence; a pleural effusion index of > 4% was considered as evidence of plasma leakage) or ascites (documented by ultrasound greater than “trace” fluid); liver injury manifested as a maximum alanine aminotransferase or aspartate aminotransferase ≥ 125 units/liter; platelet count < 100,000 cells/mm3; respiratory insufficiency with oxygen saturation < 90% as assessed by minimum O2 saturation by room-air pulse oximetry and measured on at least two occasions at least 1 minute apart; gastrointestinal hemorrhage (documented hematemesis, melena, or hematochezia); moderate to severe hemorrhage involving other sites or tissues, for example, prolonged epistaxis (requiring pressure > 15 minutes to end blood flow), oral bleeding (intermittent bleeding from gums, lips, buccal mucosa, and posterior oropharynx), widespread ecchymoses (> 5 lesions larger than 3 cm), and menometrorrhagia; altered mental status, as evidenced by disturbance of consciousness (e.g., reduced clarity of awareness of the environment; inability to focus, sustain, or shift attention) and/or a change in cognition (e.g., memory impairment, disorientation, language disturbance, or development of a perceptual disturbance); and death plausibly related to dengue. |
| Inapparent dengue infection | |
| Inapparent primary dengue | Occurrence of anti-DENV IgG seroconversion (using an indirect IgG ELISA) between two sequential sera samples obtained during scheduled visits 1 to 4. In this context, overt dengue illness was not suspected during the period in which seroconversion occurred. |
DENV = dengue virus.
*
To determine serologic status, IgM and IgG ELISA capture assays were used, where the IgG capture assay detects IgG antibodies characteristic of secondary dengue infections. Nota bene: IgG “capture conversion” only confirms that the IgG capture assay for this sample was negative according to the assay threshold.