The decline of dengue in the Americas in 2017: discussion of multiple hypotheses
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2019
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Objective Since the 1980s, dengue incidence has increased 30-fold. However, in 2017, there was a
noticeable reduction in reported dengue incidence cases within the Americas, including severe and
fatal cases. Understanding the mechanism underlying dengue’s incidence and decline in the Americas
is vital for public health planning. We aimed to provide plausible explanations for the decline in
2017.
methods An expert panel of representatives from scientific and academic institutions, Ministry of
Health officials from Latin America and PAHO/WHO staff met in October 2017 to propose
hypotheses. The meeting employed six moderated plenary discussions in which participants reviewed
epidemiological evidence, suggested explanatory hypotheses, offered their expert opinions on each
and developed a consensus.
results The expert group established that in 2017, there was a generalised decreased incidence,
severity and number of deaths due to dengue in the Americas, accompanied by a reduction in
reported cases of both Zika and chikungunya virus infections, with no change in distribution among
age groups affected. This decline was determined to be unlikely due to changes in epidemiological
surveillance systems, as similar designs of surveillance systems exist across the region. Although
sudden surveillance disruption is possible at a country or regional level, it is unlikely to occur in all
countries simultaneously. Retrospective modelling with epidemiological, immunological and
entomological information is needed. Host or immunological factors may have influenced the decline
in dengue cases at the population level through immunity; however, herd protection requires
additional evidence. Uncertainty remains regarding the effect on the outcome of sequential infections
of different dengue virus (DENV) types and Zika virus (ZIKV), and vice versa. Future studies were
recommended that examine the epidemiological effect of prior DENV infection on Zika incidence
and severity, the epidemiological effect of prior Zika virus infection on dengue incidence and severity,
immune correlates based on new-generation ELISA assays, and impact of prior DENV/other
arbovirus infection on ZIKV immune response in relation to number of infections and the duration of
antibodies in relation to interval of protection. Follow-up studies should also investigate whether
increased vector control intensification activities contributed to the decline in transmission of one or more of these arboviruses. Additionally, proposed studies should focus on the potential role of vector
competence when simultaneously exposed to various arboviruses, and on entomological surveillance
and its impact on circulating vector species, with a goal of applying specific measures that mitigate
seasonal occurrence or outbreaks.
conclusions Multifactorial events may have accounted for the decline in dengue seen in 2017.
Differing elements might explain the reduction in dengue including elements of immunity, increased
vector control, and even vector and\or viruses changes or adaptations. Most of the results of this
expert consensus group meeting are hypothetical and based on limited evidence. Further studies are
needed.
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Palavras-chave
Dengue, Decline, Americas, Hypotheses
Citação
PEREZ, Freddy et al. The decline of dengue in the Americas in 2017: discussion of multiple hypotheses. Tropical Medicine & International Health, Oxford, v. 24, n. 4, p. 442-453, 2019. DOI: 10.1111/tmi.13200. Disponível em: https://onlinelibrary.wiley.com/doi/10.1111/tmi.13200. Acesso em: 20 jan. 2025.