Dengue Fever Outbreak on Easter Island

May 24, 2018 | Emily Wolfson and Emily Cohn | Outbreak News


As of April 29, 2018, 13 cases of dengue fever have been confirmed on Easter Island [1]. The cases are assumed to have been acquired locally, as none of those affected have a history of traveling abroad. The Chilean Ministry of Health has declared a health alert to mobilize resources and work on methods of protection against the dengue vector species, Aedes aegypti. These methods include fumigation, isolation of cases, distribution of mosquito nets and spray, and elimination of hatcheries [1]. So far, all cases have been concentrated in a small area on the island. If more cases arise, the health authority of the island is prepared to do a sweeping fumigation of the whole island [2].


Dengue fever is a mosquito-borne viral infection that presents with flu-like symptoms. Approximately half the world’s population is at risk for the disease, with up to 400 million cases occurring each year. The disease is most prevalent in tropical and subtropical climates. There are four serotypes of the disease (DEN-1, DEN-2, DEN-3, and DEN-4). Humans that recover from infection by one serotype will be immune to that type for the rest of their lives [3]. All Easter Island dengue cases are DEN-1, the least lethal subtype [1].


There is no specific treatment available for dengue fever. Acetaminophen may be used to reduce fever and pain, and increased hydration is recommended to replace fluid loss from vomiting and high fever. Severe cases of dengue may require IV fluid replacement or blood transfusion. Symptoms do not usually last longer than two weeks [4]. Thus, the focus of health authorities is primarily focused on preventing spread of disease.


The first time dengue was detected on Easter Island was in 2002, and it has reappeared several times in recent years. During the first epidemic in 2002, which was also DEN-1, there were 639 reported cases. However, a predictive model used by researchers at the University of Chile showed that the true number of cases was closer to 3500, about 94% of the population at the time [5]. This suggests that the disease may be heavily underreported, and that the majority of cases were subclinical (not severe enough to report symptoms).


Underreporting and misclassification of dengue is an issue worldwide. There is a large discrepancy between cases reported by academic groups, compared to those reported to the WHO [6]. A study at the University of Notre Dame found that more than 80 percent of individuals with dengue have mild to no symptoms and have not sought treatment from a physician [7]. These individuals are contributing the most to the spread of the disease. Researchers suggest a shift towards prevention strategies that do not rely on responding to detected cases [7]. In this regard, Easter Island seems to be on the right track.











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