Overview of chikungunya epidemiology Diana P. Rojas Department of Biostatistics University of Florida November 29, 2018 Key features of transmission • Chikungunya has been identified in over 60 countries in Asia, Africa, Europe and the Americas. • Transmission mostly by Aedes aegypti and Aedes albopictus • Other mosquitoes in Africa can act as efficient vectors for chikungunya: Aedes dalzieli, Aedes furcifer, Aedes taylori, Aedes africanus, and Aedes luteocephalus. • Incubation period: 4-7 days (2-12 days). • Infectious period humans: 7 days • Extrinsic latent period: mean of 7 days (2 -9 days). • Life expectancy of the mosquitos: 30 days. Serial interval CHIKV Mosquito Mosquito feeds/acquires virus refeeds/transmits virus Extrinsic LP Intrinsic IP 7 days 3-5 days (3-12 days) Viremia Viremia Up to 7 d 0 5 8 15 18 23 Illness Illness IP: 4-7 days Human #1 Human #2 22% asymptomatic infection CHIKV Transmission cycle Weaver SC (2014) Arrival of Chikungunya Virus in the New World: Prospects for Spread and Impact on Public Health. PLoS Negl Trop Dis 8(6): e2921. doi:10.1371/journal.pntd.0002921 Factors associated with CHIKV transmission • Environmental/ecological conditions • Abundance of mosquito egg laying habitats • Completely naïve populations • Alternate vector(s), new ecological niches involved • Viral genetics / mutations • Attack rates may be explained by: • Surveillance practices • Season of CHIKV introduction into a country or a region • Vector density and activity; • Vector control measures; and lifestyle differences Key features of transmission Indicator Asia and La Reunion Americas R0 3.0-4.2 2-4 Attack Rate % 16.55 – 55.6 % 41% % Asymptomatic infections 3-22% 10-58.3% Overall seroprevalence 38.2 – 75% 13-90% CFR <1% <1% At risk groups Newborns, >55 and >45 and comorbidities comorbidities Persisting CHIKV disease 48.7% 45% Re-emergence of Chikungunya 2004-2015 Weaver SC (2014) Arrival of Chikungunya Virus in the New World: Prospects for Spread and Impact on Public Health. PLoS Negl Trop Dis 8(6): e2921. doi:10.1371/journal.pntd.0002921 1,469,912 reported cases up to December 2016. Incidence rates: 999.13 per 1,000 inhabitants. https://www.paho.org/hq/images/stories/AD/HSD/IR/Viral_Diseases/Chikungunya/CHIK V-Data-Caribbean-2017-EW-51.jpg?ua=1 COMPORTAMIENTO DENGUE – CHIK – ZIKA, años 2008-2017* Arbovirus transmission Colombia Arbovirus transmission Brazil Confirmed cases - DENV, CHKV, ZIKV in Brazil 120000 20000 18000 100000 16000 14000 80000 s 12000 e s a c s e V s K a c H 60000 10000 C DENV V d N n E a CHKV D V K I ZIKV 8000 Z 40000 6000 4000 20000 2000 0 0 CHIKV outbreaks and current transmission 2017: France and Italy 2018: Kenya and Sudan Countries with current CHIKV transmission in LA https://www.paho.org/hq/dmdocuments/2017/2017-dec-22-phe-CHIKV-cases-ew-51.pdf http://www.who.int/emergencies/diseases/chikungunya/en/ Seroprevalence studies in the Americas Saint Martin: 17% (Gay et al., 2016) Grenada: 86% (Macpherson et al., 2016) Nicaragua Managua: 13.1% (Kuan et al., 2016) Brazil Salvador: 57.1% (Dias JP et al., 2018) Mato Grosso: 20% (Cunha RV et al, 2017) India: 48% (Kawle et al., 2017) Bangladesh: 80% (Khatun et al., 2015) Benin: 36.1% (Sambri et al., 2015) Kenya 7.1% Malaysia: 5.9% – 55.6% (Azami et al., 2013; Said MA et al., 2010) Western Cameroon: 51% (Demanou et al., 2010) Singapore: 1.9% (Ang LW et al., 2017) Mozambique: 26.4% (Gudo et al., 2015) Mayotte: 37.2% (Sissoko, 2008) Grande Comore Island: 63% (Sergon et al., 2007) La Reunion: 40% (Gerardin P. et al., 2008) French Polynesia, 2014–2015: 76% Conclusions • Chikungunya virus has endemic transmission in some countries in Latin America and Southeast Asia. • CHIKV transmission is heterogenous between and within countries and regions. • More seroprevalence studies for CHIKV are needed to understand better the impact of previous outbreaks and endemic circulation. • The estimated R0 of CHIKV is from 2-4: attack rates 16-55%. • The real burden of CHIKV is unknown. .