Dengue, Zika and Chikungunya: Emerging Arboviruses in the New World

Abstract

The arboviruses that cause dengue, chikungunya, and Zika illnesses have rapidly expanded across the globe in recent years, with large-scale outbreaks occurring in Western Hemisphere territories in close proximity to the United States (U.S.). In March 2016, the Centers for Disease Control and Protection (CDC) expanded its vector surveillance maps for A. aegypti and A. albopictus, the mosquito vectors for these arboviruses. They have now been shown to inhabit a larger portion of the U.S., including the heavily populated northeast corridor. Emergency physicians need to further familiarize themselves with these diseases, which have classically been considered only in returning travelers but may soon be encountered in the U.S. even in the absence of travel. In this paper, we discuss the presentation and treatment of dengue, Zika, and chikungunya, as well as special challenges presented to the emergency physician in evaluating a patient with a suspected arbovirus infection.

Figure 1

Map showing the estimated global distribution of dengue, Zika, and chikungunya.

Figure 2a,b

In April 2015, the CDC updated its vector surveillance maps to depict that both A. aegypti and A. albopictus are now believed to inhabit a wider range of distribution in the U.S. Figure 2a illustrates the expansion of territory covered by A. aegypti; Figure 2b illustrates the expansion of A. albopictus. The range of both mosquitos has spread significantly to the north and west. Although the significance of this expansion in epidemiologic terms is unclear, it may place a greater proportion of the population at risk for exposure to emerging arboviruses such as Zika, particularly during warmer months.

Figure 3

Three distinct phases of dengue infection have been described: incubation, febrile, and recovery. The critical phase, when patients may become unstable, typically occurs after defervescence of the fever. Although most patients will improve after the febrile stage, those who progress to the critical phase may display warning signs. By closely monitoring for these signs, clinicians can identify and appropriately disposition patients at higher risk for a more severe clinical course. The laboratory evaluation of dengue also varies based on the stage of infection and thus samples evaluating for both viral practices (PCR or NS1) and IgM levels should be ordered. DENV, dengue virus; NS1, nonstructional protein 1; PCR, polymerase chain reaction *PCR is expressed on the surface of infected cells.

Figure 4

Management algorithm for dengue, adapted from Dengue Case Management, available at: http://www.cdc.gov/dengue/resources/DENGUE-clinician-guide_508.pdf. HCT, hematocrit; AST, aspartate amino transferase; ALT, amino alanine transferase; ICU, intensive care unit AST/ALT values are in units/liter.

Figure 5

The tourniquet test, which is a marker of capillary fragility, is a quick and easy bedside study that can help physicians differentiate dengue from other illnesses, although it lacks both sensitivity and specificity. A blood pressure cuff is inflated to midway between the systolic and diastolic blood pressure and maintained for five minutes. A positive test is the presence of 10 or more petechiae per square inch. 16,19.

Figure 6

Rash on a patient with Zika infection.

Figure 7

Proposed testing algorithm for the initial evaluation of a patient with suspected arbovirus infection. Depending on the region of travel, malaria and other native pathogens such as typhoid and leptospirosis also should be considered. POC, point of care; CBC, complete blood count; LFTs, liver function tests, PT/PTT, prothrombin time/partial thromboplastin time; UA/Hcg, urinalysis/human chorionic gonadotropin, CXR, chest x-ray; PCR, polymerase chain reaction