2017 dengue outbreak in Sri Lanka explained

2017 dengue outbreak in Sri Lanka
Disease:	Dengue fever
Virus Strain:	Dengue virus
Dates:	May 2017 – Aug 2017
Origin:	Sri Lanka
Type:	DENV-2
Confirmed Cases:	186,101
Deaths:	440
Vaccinations:	no vaccine available (at time)

In 2017, there was a rise in the number of dengue fever cases reported in the island country of Sri Lanka. The peak of the outbreak occurred during the mid-year monsoon season, with more than 40,000 cases reported in July alone, far exceeding historical highs. By the end of the year, the total number of dengue cases had risen to 186,101.^[1]

Most cases (43%) were recorded in urban areas of the Western Province, such as the Colombo district.^[2] The majority of dengue cases affected young people and school children. By the end of the year, the total number of dengue-related deaths reached 440.

Background

In 2017, Sri Lanka experienced its largest outbreak of dengue fever, a neglected tropical disease, since the first recorded case in 1962.^{[3] [4] [5]} This biological hazard, transmitted via female mosquito bites, resulted in 186,101 dengue cases, a significant increase compared to previous years (see table 2), and let to 440 deaths.^{[6] [7] [8]}

Year! scope="row"

Number of cases
2010	34,188
2011	28,473
2012	44,461
2013	32,063
2014	47,502
2015	29,777
2016	50,592
2017	186,101
2018	51,659
2019	105,049
2020	31,162
2021	25,067
2022	57,864

Outbreak

Sri Lanka's Ministry of Health (MoH) reported an increase in dengue fever cases from January, peaking in July. The Majority of cases were concentrated in the western and northern parts of the country, particularly in the urban Colombo district.

Area! scope="row"

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Total
Sri Lanka	10,927	8,724	13,540	12,540	15,963	25,319	41,121	22,270	9,519	6,614	8,868	10,753	186,158
Colombo District	2,734	1,900	2,467	2,570	3,333	5,372	7,471	3,620	1,251	823	1,131	1,602	34,274
Gampaha District	1,635	1,087	1,870	2,072	3,168	4,901	9,039	3,553	1,246	779	1,078	1,219	31,647
Kalutara District	581	448	836	739	946	1,248	2,612	1,477	663	337	528	546	10,961

The Government of Sri Lanka spent over US$12 million on outbreak control efforts, with support from NGOs like the Red Cross.^{[9] [10]}

Causes

Climate

• Sri Lanka's tropical climate offers prime mosquito breeding conditions.^[11]
• The 2017 monsoon rains (May–August) coincided with the peak of the dengue outbreak (table 2). Triggering floods and disrupting refuse collection, increasing mosquito breeding sites.^[12]
• However, annual rainfall and El Nino conditions were lower on average than previous years, suggesting that climate was not completely responsible for the outbreak.

Political

• MoH failed to prepare and take appropriate mosquito vector control.^[13]
• Insufficiencies in the virologic surveillance program failed to identify dengue serotypes and genotypes.^[14] Leaving Sri Lanka unprepared for new strains (DENV-2), for which their population would have little immunity.

Socio-economic

• Sri Lanka is a middle-income country with a GDP per capita of US $12,600 (2017).^[15] This restricts investment in healthcare infrastructure resulting in an overstretched healthcare system.
• High urban population density in western districts created higher probability of transmission.
• In 2017, 42% of Sri Lankans were in extreme poverty (below US$5.50 a day) which limits a family's access to healthcare and increases risk of disease.^[16]
• Regional disparities, due to the Sri Lankan civil conflict (1983-2009), displaced people to IDP camps and marginalized ethnic groups (Tamils) in north and eastern districts, reducing support and increasing disease risk.^{[17] [18]}

Impacts

Short-term impacts

• Unexpected high death toll.
• Disruption to workplaces, household income, and education as the majority of cases were of people aged 10–29.
• Direct and indirect impacts of the dengue outbreak affected 600,000 people, in all 25 districts, prominently in urban areas. However, some districts may have been under-reported due to ethnic marginalization and the presence of IDP camps.^[19]
• Dengue treatment strained national economic resources costing Sri Lanka US $12.7 million (LKR 1.938 billion).

Long-term impacts

• Today dengue cases are declining in Sri Lanka, with 25,067 total cases in 2021 (table 1).
• Dengue is still present with new strains (serotypes DENV-3 and DENV-4) becoming more prominent threatening future outbreaks.
• Combined with the COVID-19 pandemic there is still immense pressures on healthcare and trade networks.^[20]
• 2022 has seen an economic crisis and severe food insecurity in Sri Lanka, the dengue outbreak would be a contributing factor.^{[21] [22]}

Future

Climate change models suggest that Sri Lanka's climate is becoming more conducive to mosquito breeding, this combined with economic instability could trigger a future epidemic.^[23] There is a possibility of a cycle of disease, poverty and food insecurity which may be challenging to break.^[24] However, this could be mitigated if the MoH, supported by institutions like WHO, engage in proactive strategies. A licensed vaccine (Dengvaxia) is now available, at the cost of US$78 per person - with five more in development. However, Sri Lanka's current expenditure is US$161 per capita on healthcare (2021), the vaccine is a significant proportion of that budget and in uncertain economic times may not be a priority.^{[25] [26]}

See also

• Dengue fever outbreaks
• Neglected Tropical Diseases
• Tropical disease
• Mosquito-borne disease

External links

• WHO: Sri Lanka
• Ministry of Health - Sri Lanka
• Epidemiology Unit

References

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7101108/
2. Web site: WHO Dengue fever – Sri Lanka. https://web.archive.org/web/20170721165901/http://www.who.int/csr/don/19-july-2017-dengue-sri-lanka/en/. July 21, 2017. 2020-11-27. WHO.
3. Web site: 2022-03-07 . CDC - Neglected Tropical Diseases - Diseases . 2022-10-28 . www.cdc.gov . en-us.
4. Ngwe Tun . Mya Myat . Muthugala . Rohitha . Nabeshima . Takeshi . Rajamanthri . Lakmali . Jayawardana . Dulani . Attanayake . Shanthi . Soe . Aung Min . Dumre . Shyam Prakash . Ando . Tsuyoshi . Hayasaka . Daisuke . Inoue . Shingo . Buerano . Corazon C. . Morita . Kouichi . 2020-04-01 . Unusual, neurological and severe dengue manifestations during the outbreak in Sri Lanka, 2017 . Journal of Clinical Virology . en . 125 . 104304 . 10.1016/j.jcv.2020.104304 . 32145478 . 212629415 . 1386-6532.
5. Ali . Shahid . Khan . Abdul Waheed . Taylor-Robinson . Andrew W. . Adnan . Muhammad . Malik . Shahana . Gul . Saba . June 2018 . The unprecedented magnitude of the 2017 dengue outbreak in Sri Lanka provides lessons for future mosquito-borne infection control and prevention . Infection, Disease & Health . en . 23 . 2 . 114–120 . 10.1016/j.idh.2018.02.004. 80605119 . free . 38715304 .
6. Tissera . Hasitha A. . Jayamanne . Bernard D.W. . Raut . Rajendra . Janaki . Sakunthala M.D. . Tozan . Yesim . Samaraweera . Preshila C. . Liyanage . Prasad . Ghouse . Azhar . Rodrigo . Chaturaka . de Silva . Aravinda M. . Fernando . Sumadhya D. . April 2020 . Severe Dengue Epidemic, Sri Lanka, 2017 . Emerging Infectious Diseases . 26 . 4 . 682–691 . 10.3201/eid2604.190435 . 1080-6040 . 7101108 . 32186490.
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9. Web site: 21 August 2018 . Sri Lanka: Dengue Outbreak - Jul 2017 . 2020-11-27 . ReliefWeb . en.
10. Dengue Fever Outbreak in Sri Lanka Kills Nearly 300 People . 2020-11-27 . Time.
11. Web site: Dengue and severe dengue . 2022-10-28 . www.who.int . en.
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13. Tissera . H. A. . Samaraweera . P. C. . Jayamanne . B. D. W. . Janaki . M. D. S. . U Chulasiri . M. P. P. . Rodrigo . C. . Fernando . S. D. . February 2018 . Use of Bacillus thuringiensis israelensis in integrated vector control of Aedes sp. in Sri Lanka: a prospective controlled effectiveness study . Tropical Medicine & International Health . en . 23 . 2 . 229–235 . 10.1111/tmi.13015. 29164802 . 5071742 . free . 1959.4/unsworks_48835 . free .
14. Ngwe Tun . Mya Myat . Muthugala . Rohitha . Rajamanthri . Lakmali . Nabeshima . Takeshi . Buerano . Corazon C. . Morita . Kouichi . 2021-09-30 . Emergence of Genotype I of Dengue Virus Serotype 3 during a Severe Dengue Epidemic in Sri Lanka in 2017 . Japanese Journal of Infectious Diseases . en . 74 . 5 . 443–449 . 10.7883/yoken.JJID.2020.854 . 33642435 . 232078010 . 1344-6304. free .
15. Web site: Gapminder Tools . 2022-10-28 . www.gapminder.org . en.
16. Web site: WHO . 2017 . World Bank and WHO: Half the world lacks access to essential health services, 100 million still pushed into extreme poverty because of health expenses . 2022-10-28 . www.who.int . en.
17. Web site: 2019-06-19 . Sri Lanka - World Directory of Minorities & Indigenous Peoples . 2022-10-28 . Minority Rights Group . en-GB.
18. Web site: Kapila . Mukesh . 2018 . Healthcare in Conflict Settings . 2022-10-28 . World Innovation Summit for Health . en-US.
19. Book: Advances in Parasitology: Important Helminth Infections in Southeast Asia: Diversity and Potential for Control and Elimination. Part A . 2010 . Xiao-Nong Zhou . Robert Bergquist . Remigio Olveda . Jürg Utzinger . 978-0-12-381956-7 . London . 689053662.
20. Web site: WHO . 2022 . Vaccines and immunization: Dengue . 2022-10-28 . www.who.int . en.
21. Web site: Root & Win . 2022-08-09 . How Sri Lanka went from topping Lonely Planet's list to almost 30% hunger levels . 2022-10-28 . The New Humanitarian . en.
22. Web site: Quiggin . John . Mallawaarachchi . Thilak . How did Sri Lanka run out of money? 5 graphs that explain its economic crisis . 2022-10-28 . The Conversation . 25 July 2022 . en.
23. Bhatia . Surbhi . Bansal . Dhruvisha . Patil . Seema . Pandya . Sharnil . Ilyas . Qazi Mudassar . Imran . Sajida . 2022 . A Retrospective Study of Climate Change Affecting Dengue: Evidences, Challenges and Future Directions . Frontiers in Public Health . 10 . 884645 . 10.3389/fpubh.2022.884645 . free . 2296-2565 . 9197220 . 35712272.
24. Yngve . Agneta . Margetts . Barrie . Hughes . Roger . Tseng . Marilyn . November 2009 . Food insecurity – not just about rural communities in Africa and Asia . Public Health Nutrition . en . 12 . 11 . 1971–1972 . 10.1017/S1368980009991650 . 19814853 . free . 1475-2727.
25. Web site: Current health expenditure (% of GDP) - Sri Lanka Data . 2022-10-28 . data.worldbank.org.
26. Pearson . Carl A. B. . Abbas . Kaja M. . Clifford . Samuel . Flasche . Stefan . Hladish . Thomas J. . August 2019 . Serostatus testing and dengue vaccine cost–benefit thresholds . Journal of the Royal Society Interface . en . 16 . 157 . 20190234 . 10.1098/rsif.2019.0234 . 1742-5689 . 6731500 . 31431184.