International Journal of Infectious Diseases 110 (2021) 417–425 Contents lists available at ScienceDirect International Journal of Infectious Diseases journal homepage: www.elsevier.com/locate/ijid Transient transmission of Chikungunya virus in Singapore exemplifies successful mitigation of severe epidemics in a vulnerable population Hapuarachchige Chanditha Hapuarachchi 1,£,∗ , Wing-Yan Wong 1,£ , Carmen Koo 1 , Wei-Ping Tien 1 , Gladys Yeo 1 , Jayanthi Rajarethinam 1 , Eugene Tan 1 , Suzanna Chiang 1 , Chee-Seng Chong 1 , Cheong-Huat Tan 1 , Li-Kiang Tan 1,¶ , Lee-Ching Ng 1,2 1 Environmental Health Institute, National Environment Agency, 11, Biopolis Way, #06-05-08, Singapore 138667 2 School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551 a r t i c l e i n f o Article history: Received 10 June 2021 Revised 2 August 2021 Accepted 4 August 2021 Keywords: Chikungunya virus genotyping seroprevalence Aedes surveillance control a b s t r a c t Objectives: Singapore experienced two major outbreaks of chikungunya in 2008-09 and 2013-14. Despite repeated virus introductions, fresh local outbreaks have not emerged after 2014. The present study re- views the success of chikungunya control in Singapore, despite repeated introduction of virus strains, presence of competent vectors and an immunologically naïve population. Methods: Chikungunya virus (CHIKV) sequences (421 envelope 1 genes and 56 polyproteins) were anal- ysed to distinguish the indigenous virus groups from 2008 to 2020. Vector surveillance data was used to incriminate the vector/s associated with local outbreaks. The population exposure to CHIKV was deter- mined by assessing the seroprevalence status in three cohorts of sera collected in 2009 (n=2,008), 2013 (n=2,000) and 2017 (n=3,615). Results: Four distinct groups of CHIKV of East, Central and South African genotype have mainly circulated since 2008, transmitted primarily by Aedes albopictus. The age weighted CHIKV IgG prevalence rates were low (1-5%) and showed a non-significant increase from 2009 to 2013, but a significant decrease in 2017. In contrast, the prevalence of CHIKV neutralising antibodies in the population increased significantly from 2009 to 2013, with no significant change in 2017, but the levels remained below 2%. Conclusions: The evidence suggested that surveillance and vector control strategies implemented were robust to avert severe epidemics, despite repeated introduction of virus strains, presence of competent vectors and an immunologically naïve population. © 2021 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Background Chikungunya virus (CHIKV) is a mosquito-borne alphavirus of the Togaviridae family. CHIKV causes periodic, but explosive epi- demics. The most notable recent epidemics occurred in the Indian Abbreviations: BEAST, Bayesian Evolutionary Analysis by Sampling Trees; BHK, Baby Hamster Kidney; CHIKV, Chikungunya virus; E1, Envelope 1; ECSA, East, Cen- tral and South African; EHI, Environmental Health Institute; GTR, General time reversible; MOH, Ministry of Health; NEA, National Environment Agency; PRNT, Plaque reduction neutralisation test; RT-PCR, Reverse transcription polymerase chain reaction. ∗ Correspondence. E-mail address: [email protected] (H.C. Hapuarachchi). £ Equal first authorship. ¶ Current address: National Centre for Food Science, Singapore Food Agency, 10, Perahu Road, Singapore 718837. Ocean islands (Schuffenecker et al., 2006), India (Arankalle et al., 2007), Southeast Asia (Hapuarachchi et al., 2009, Rianthavorn et al., 2010, Somlor et al., 2017) and the Americas (Leparc-Goffart et al., 2014, Morrison, 2014), causing millions of infections. The explo- sive nature of these epidemics has demonstrated how difficult it is to contain CHIKV spread by relying mainly on vector con- trol measures, in the absence of therapeutics and vaccines. Be- sides grave implications on public health, chikungunya epidemics have inflicted a heavy economic burden in affected countries (Feldstein et al., 2019, Hossain et al., 2018). Therefore, the success- ful control of chikungunya is important to avert devastating epi- demics in endemic countries. Indigenous transmission of CHIKV was first reported in Singa- pore in 2008 (Leo et al., 2009). Singapore has experienced two large outbreaks since then, but cases have largely been imported and sporadic after the last outbreak in 2014 (Oon and Ng, 2014a). https://doi.org/10.1016/j.ijid.2021.08.007 1201-9712/© 2021 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
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