Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 Jun 10;15(6):e0009420.
doi: 10.1371/journal.pntd.0009420. eCollection 2021 Jun.

The impact of COVID-19 lockdown on dengue transmission in Sri Lanka; A natural experiment for understanding the influence of human mobility

Prasad Liyanage  1   2 , Joacim Rocklöv  3 , Hasitha Aravinda Tissera  2
Affiliations

The impact of COVID-19 lockdown on dengue transmission in Sri Lanka; A natural experiment for understanding the influence of human mobility

Prasad Liyanage et al. PLoS Negl Trop Dis. .

Abstract

Background: Dengue is one of the major public health problems in Sri Lanka. Its outbreak pattern depends on a multitude of drivers, including human mobility. Here we evaluate the impact of COVID-19 related mobility restriction (lockdown) on the risk of dengue in Sri Lanka.

Methodology: Two-stage hierarchical models were fitted using an interrupted time-series design based on the notified dengue cases, January 2015 to July 2020. In the first stage model, the district level impact was estimated using quasi-Poisson regression models while accounting for temporal trends. Estimates were pooled at zonal and national levels in the second stage model using meta-analysis. The influence of the extended period of school closure on dengue in children in the western province was compared to adults.

Findings: Statistically significant and homogeneous reduction of dengue risk was observed at all levels during the lockdown. Overall an 88% reduction in risk (RR 0.12; 95% CI from 0.08 to 0.17) was observed at the national level. The highest impact was observed among children aged less than 19 years showing a 92% reduction (RR 0.8; 95% CI from 0.03 to 0.25). We observed higher impact in the dry zone having 91% reduction (RR 0.09; 95% CI from 0.05 to 0.15) compared to wet zone showing 83% reduction (RR 0.17; 95% CI from 0.09 to 0.30). There was no indication that the overall health-seeking behaviour for dengue had a substantial influence on these estimates.

Significance: This study offers a broad understanding of the change in risk of dengue during the COVID-19 pandemic and associated mobility restrictions in Sri Lanka. The analysis using the mobility restrictions as a natural experiment suggests mobility patterns to be a very important driver of dengue transmission.

PubMed Disclaimer

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Distribution of dengue cases per 100,000 population during first and second quarters within administrative districts in Sri Lanka.
(A) Averaged dengue cases from 2015 during 1st quarter. (B) Five-year average during and 2nd quarter. (C) Observed cases during first quarter 2020. (D) Observed cases during second quarter 2020 per 100,000 population in Sri Lanka. Source of the base file: https://data.humdata.org/dataset/sri-lanka-administrative-levels-0-4-boundaries.
Fig 2
Fig 2. Reported dengue cases during 2020 compared to monthly averaged dengue cases reported from 2015 to 2019 averaged across all districts in climate zones in Sir Lanka.
(A) Wet zone. (B) Dry zone. The green solid line shows the five-year average. Red dashed line shows cases reported during 2020. The purple solid area indicates the period of extensive mobility restriction; the purple dashed area indicates the period of school closure; the pink area indicates the period of routine dengue outbreak control interventions. The residential mobility represents the percentage change of daily mobility compared to the baseline residential mobility; the workplace mobility represents the percentage change in daily mobility compared to the baseline workplace mobility.
Fig 3
Fig 3. Reported dengue cases among children and adults during 2020 compared to monthly averaged dengue cases reported from 2015 to 2019 averaged across all districts in the western province in Sir Lanka.
The green solid line shows the five-year average. Red dashed line shows cases reported during 2020.The blue and orange dashed lines indicate the monthly average number of dengue cases among children (age 0 to 19 years) and adults (age more than 20 years) reported respectively in 2020. The purple solid area indicates the period of extensive mobility restriction; the purple dashed area indicates the period of school closure; the pink area indicates the period of routine dengue outbreak control interventions. The residential mobility represents the percentage change of daily mobility compared to the baseline residential mobility; the workplace mobility represents the percentage change in daily mobility compared to the baseline workplace mobility.
Fig 4
Fig 4. Time series plot of observed and estimated dengue cases from 2015 to 2020 July in wet and dry zones in Sri Lanka.
(A) Wet zone. (B) Dry zone. The green line represents observed dengue cases. Blue dashed line represents the model predicted or estimated dengue cases with the lockdown intervention in place. The red dashed line represents estimated dengue cases without intervention or the counterfactual estimation. The grey zone indicates the lower and upper limits of the 95% confidence intervals for estimated dengue cases at each month.
See this image and copyright information in PMC

References

    1. Comprehensive Guideline for Prevention and Control of Dengue and Dengue Haemorrhagic Fever. Revised and expanded edition (2011). [Internet]. SEARO Publications. 2011. Available from: https://apps.who.int/iris/handle/10665/204894
    1. Bhatt S, Gething PW, Brady OJ, Messina JP, Farlow AW, Moyes CL, et al.. The global distribution and burden of dengue. Nature [Internet]. 2013. Apr 25 [cited 2020 Oct 30];496(7446):504–7. Available from: https://www.nature.com/articles/nature12060 doi: 10.1038/nature12060 - DOI - PMC - PubMed
    1. Stanaway JD, Shepard DS, Undurraga EA, Halasa YA, Coffeng LE, Brady OJ, et al.. The global burden of dengue: an analysis from the Global Burden of Disease Study 2013. Lancet Infect Dis [Internet]. 2016 Jun 1 [cited 2020 Oct 30];16(6):712–23. Available from: http://www.thelancet.com/article/S1473309916000268/fulltext - PMC - PubMed
    1. Rodriguez-Morales AJ, Gallego V, Escalera-Antezana JP, Méndez CA, Zambrano LI, Franco-Paredes C, et al.. COVID-19 in Latin America: The implications of the first confirmed case in Brazil [Internet]. Vol. 35, Travel Medicine and Infectious Disease. Elsevier; USA; 2020. [cited 2020 Oct 30]. Available from: https://pubmed.ncbi.nlm.nih.gov/32126292/ - PMC - PubMed
    1. World Health Organization. Epidemiological Update: Dengue and other Arboviruses—10 June 2020—PAHO/WHO | Pan American Health Organization; [Internet]. [cited 2020 Oct 30]. Available from: https://www.paho.org/en/documents/epidemiological-update-dengue-and-othe...

Publication types