Accuracy of Zika virus disease case definition during simultaneous Dengue and Chikungunya epidemics

Abstract

BackgroundZika is a new disease in the American continent and its surveillance is of utmost importance, especially because of its ability to cause neurological manifestations as Guillain-Barré syndrome and serious congenital malformations through vertical transmission. The detection of suspected cases by the surveillance system depends on the case definition adopted. As the laboratory diagnosis of Zika infection still relies on the use of expensive and complex molecular techniques with low sensitivity due to a narrow window of detection, most suspected cases are not confirmed by laboratory tests, mainly reserved for pregnant women and newborns. In this context, an accurate definition of a suspected Zika case is crucial in order for the surveillance system to gauge the magnitude of an epidemic.MethodologyWe evaluated the accuracy of various Zika case definitions in a scenario where Dengue and Chikungunya viruses co-circulate. Signs and symptoms that best discriminated PCR confirmed Zika from other laboratory confirmed febrile or exanthematic diseases were identified to propose and test predictive models for Zika infection based on these clinical features.Results and discussionOur derived score prediction model had the best performance because it demonstrated the highest sensitivity and specificity, 86·6% and 78·3%, respectively. This Zika case definition also had the highest values for auROC (0·903) and R2 (0·417), and the lowest Brier score 0·096.ConclusionsIn areas where multiple arboviruses circulate, the presence of rash with pruritus or conjunctival hyperemia, without any other general clinical manifestations such as fever, petechia or anorexia is the best Zika case definition.

Burden of dengue among febrile patients at the time of chikungunya introduction in Piedecuesta, Colombia

“…This passive facility‐based fever surveillance conducted in Piedecuesta – Colombia allowed identification of incident arboviral diseases in more than half of the participants ( n = 486; 58%), of which 60% ( n = 295) were dengue cases. Although the distribution of these diseases could vary according to the setting and the time when the study was conducted , this finding aligns with the documented predominant presence of DENV in the study area, and the introduction of CHIKV around the study period .…”

“…Compared to dengue, chikungunya was less commonly identified, which is similar to what was reported in Brazil between 2014–2016, and the differences could be attributed to the time and duration of each study . Chikungunya was introduced in the Americas in late 2013, in Colombia in mid 2014, and our study was conducted from mid‐2014 to mid‐2015.…”

“…The presence of all four serotypes in the study area, even at the time of chikungunya introduction, confirms an ongoing dengue presence and its endemicity. Although the frequency distribution of dengue serotypes will in general depend of multiple factors including the viral load, patient's DOF, and the method used for identification , the higher frequency of DENV1 observed in our study was also observed in other studies conducted in the Americas around the same period , which could be associated with a regional pattern of dengue distribution .…”

“…On the other hand, chikungunya cases were more likely to occur in older participants, mostly among people in the 21–40 year age group. This same pattern of age distribution has been observed in an acute febrile illness survey (AFI) conducted in Puerto Rico , and in a cross‐sectional study in Brazil . Possible explanations include the consideration that older people were susceptible to the recently introduced chikungunya and that older participants were already sensitised by the endemic presence of dengue .…”

“…This could be explained by the adequate performance of the rapid tests in this setting, and the likelihood of clinicians to rely on such a test when they have access to them . Thrombocytopaenia and abdominal pain however, were significant and consistent predictors throughout the entire set of our analysis, indicating that regardless of the presence or performance of RDTs, these factors are essential predictors of dengue identification in the clinical practice .…”