Abstract
SummaryBackground: In response to the COVID-19 pandemic, China implemented strict restrictions on cross-border travel to prevent disease importation. Yunnan, a Chinese province that borders dengue-endemic countries in Southeast Asia, experienced unprecedented reduction in dengue, from 6840 recorded cases in 2019 to 260 in 2020.Methods: Using a combination of epidemiological and virus genomic data, collected from 2013 to 2020 in Yunnan and neighbouring countries, we conduct a series of analyses to characterise the role of virus importation in driving dengue dynamics in Yunnan and assess the association between recent international travel restrictions and the decline in dengue reported in Yunnan in 2020.Findings: We find strong evidence that dengue incidence between 2013-2019 in Yunnan was closely linked with international importation of cases. A 0-2 month lag in incidence not explained by seasonal differences, absence of local transmission in the winter, effective reproductive numbers < 1 (as estimated independently using genetic data) and diverse cosmopolitan dengue virus phylogenies all suggest dengue is non-endemic in Yunnan. Using a multivariate statistical model we show that the substantial decline in dengue incidence observed in Yunnan in 2020 but not in neighbouring countries is closely associated with the timing of international travel restrictions, even after accounting for other environmental drivers of dengue incidence.Interpretation: We conclude that Yunnan is a regional sink for DENV lineage movement and that border restrictions may have substantially reduced dengue burden in 2020, potentially averting thousands of cases. Targeted testing and surveillance of travelers returning from high-risk areas could help to inform public health strategies to minimise or even eliminate dengue outbreaks in non-endemic settings like southern China.Funding: Funding for this study was provided by National Key Research and Development Program of China, Beijing Science and Technology Planning Project (Z201100005420010); Beijing Natural Science Foundation (JQ18025); Beijing Advanced Innovation Program for Land Surface Science; National Natural Science Foundation of China (82073616); Young Elite Scientist Sponsorship Program by CAST (YESS) (2018QNRC001); H.T., O.P.G. and M.U.G.K. acknowledge support from the Oxford Martin School. O.J.B was supported by a Wellcome Trust Sir Henry Wellcome Fellowship (206471/Z/17/Z).Chinese translation of the abstract (Appendix 2)
Highlights
Dengue is responsible for 10,000 deaths annually[1] and is responsible for the largest burden of all the arboviral diseases, with an estimated 100 million symptomatic infections per year globally.[2]
We were unable to assess the correlation between dengue cases in Yunnan with those in Myanmar in 2020 as data was not available form this country at the time of analysis. These analyses show that Yunnan has seen a much bigger decline and disruption of dengue dynamics in 2020 than its regional neighbours and that this decline is significantly associated with the timing of border restrictions
Using a combination of epidemiological and phylogenetic data we show that Dengue virus (DENV) transmission in Yunnan is only made possible by frequent re-introduction
Summary
Dengue is responsible for 10,000 deaths annually[1] and is responsible for the largest burden of all the arboviral diseases, with an estimated 100 million symptomatic infections per year globally.[2] The number of dengue cases reported to WHO has increased over 8 fold over the last two decades, from 0.5 million in 2000, to > 2.4 million in 2010, and to 4.2 million in 20193 and it has been estimated that over 6.1 billion people might be at risk of dengue by 2080.4 Dengue virus (DENV) is a mosquito-borne virus and a member of the Flaviviridae family.[5,6] Vector control and community engagement remain the main strategies to reduce dengue burden. Even small numbers of imported dengue cases, i.e. DENV introductions, can trigger locally acquired infections and even local outbreaks.[8]. A Chinese province that borders dengue-endemic countries in Southeast Asia, experienced unprecedented reduction in dengue, from 6840 recorded cases in 2019 to 260 in 2020
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