Chikungunya virus infections in Finnish travellers 2009-2019

Figures & data

Table 1. Demographic data and laboratory findings from patients with acute CHIKV disease during years 2009–2019.

Year	Sex (f/m)	Age (yEARS)	Travel history	Symptoms	Travel month; Sample taken days/weeks/months after onset of symptoms	Total Ab HI (titer)/IgG IFA:pos/neg (titer)	ELISA IgM (Euroimmun), pos ≥1.1	RT-qPCR neg/pos (Ct)	NGS/sequencing etc INFO
2009	f	28	Thailand (Asia)	Fever, rash, joint pain	June; >1 week	HI: 320	6.4	neg	ND
	f	41	NA	Joint pain, joint swelling	June; NA	HI: 320	2.6	neg	ND
	f	41	Singapore (Asia)	Fever, rash, mosquito bites	June; >1 week	HI: 160	ND	neg	ND
2010	m	27	Indonesia (Asia)	Fever [21]	November; <1 week	HI:2560	6.3	pos, Ct 34.01	Sequencing carried out by 21
2011	No cases reported
2012	f	34	Papua New Guinea (Oceania)	Typical symptoms of CHIKV infection (not specified in more detail)	December, 2012; ~4 months	HI:80	2.9	ND	ND
2013	No cases reported
2014	m	56	The Philippines (Asia)	NA	January; ~2 months	HI:320	3.2	ND	ND
	m	27	Grenada (Caribbean)	Fever, PNS symptoms, swollen lymph nodes	September; <1 week	HI:20	7.2	pos, Ct 41	RT-qPCR product was sequenced: CHIKV; sequencing using nested-RT-PCR/NGS or isolation not successful
	f	32	Jamaica (Caribbean)	NA	November; <1 week	HI:20	7.4	pos, Ct 31.7	Sequencing: CHIKV; Isolation not successful
					November; 15 days	HI:160	7.2	ND	ND
	m	33	Jamaica (Caribbean)	NA	November; <1 week	HI:<20	<1.1	pos, Ct 27.8	Sequencing/NGS: Whole CHIKV genome; Isolation attempts not succeeded.
					November; 17 days	HI:160	7.6	ND	ND
2015	f	33	Thailand (Asia)	Fever, rash, thrombocytopenia	January; >1 week	HI:160	1.1	neg	ND
	m	56	Indonesia and Bali, Singapore (Asia)	High fever (fluctuating), joint pain, rash	January; ~1 wk	HI:160	5.7	pos, Ct 34.9	RT-qPCR product was sequenced: CHIKV; sequencing using nested-RT-PCR/NGS or isolation not successful
	f	30	NA	NA	NA; NA (sample taken in April)	HI: 640	6.3	neg	ND
	f	29	Mexico (Caribbean coast)	Joint pain, tired	July; >1 week	HI: 1280	7.7	neg	ND
	f	48	Cuba (Caribbean)	Fever	November; >3 weeks	HI:320	6.5	neg	ND
	m	51	NA	NA	NA; NA (sample taken in December)	HI:640	6.3	neg	ND
2016	No cases reported
2017/ 2018*	m	24	NA	NA	NA; NA (sample taken in June)	IFA:640	5.6	neg	ND
	m	25	Bangladesh (Asia)	Fever, itchy skin, joint pain, stomach ache	July; >2 weeks	IFA:1280	3.3	neg	ND
	m	31	Bangladesh (Asia)	Typical symptoms for CHIKV infection (not specified in more detail)	June and July; >3 weeks	IFA: >1280	7.2	neg	ND
	m	54	Bangladesh (Asia)	Fever, joint pain	June; >4 weeks	IFA:1280	4.0	neg	ND
	m	47	The Phillippines (Asia)	NA	December 2017/January 2018; >2 weeks	IFA:2560	4.9	neg	ND
2018
2019	f	43	Thailand (Asia)	NA	January; NA	ND	ND	pos, Ct 24.54	Sequencing: CHIKV; Isolation not successful. NGS not performed
					January; >3 months (sample taken in April)	IFA: >2560	1.2	neg	ND
	f	35	Thailand (Asia)	NA	January; NA	IFA: >2560	6.4	neg	ND
	f	13	Thailand (Asia)	Fever, septic shock suspected, rash, arthralgia; treated in ICU in Thailand [34]	February; 11 days	IFA: >2560	7.1	pos, Ct 35.47	Serology and symptoms described in 34, sequencing and isolation not successful.
	f	49	Thailand [Asia)	Fever, joint pain, diarrhoea, rash	February; 10 days	IFA: >2560	6.9	pos, Ct 35.64	Serology and symptoms described in 34, sequencing and isolation not successful.
	m	9	Thailand [Asia]	Fever, rash, arthralgia, diarrhoea, underlying disease: type 1 diabetes	February; 11 days	IFA: >2560	7.3	pos, Ct 36.31	Serology and symptoms described in 34, sequencing and isolation not successful.
	m	70	Thailand [Asia]	Fever, arthralgia, polyarthritis, tenosynovitis, itching without rash, underlying disease: type 2 diabetes, hypertension, cardiovascular disease	February; >3 weeks	IFA: 1280	2.9	neg	Serology and symptoms described in 34
	m	47	Thailand (Asia]	Fever, arthralgia, strong pain in heels [inability to walk), itching without rash	February; >3 weeks	IFA: >2560	3.7	neg	Serology and symproms described in 34
	f	52	Thailand and Phuket (Asia]	Fever, joint pain	February; <1 week	IFA: <10	<1.1	pos, Ct 28.6	Sequencing/NGS: Whole CHIKV genome; CHIKV isolation.
					February; >2 months (sample taken in April)	IFA: >2560	3.2	ND	ND
	m	51	Thailand and Phuket (Asia)	Fever, rash, mild conjuctivitis, arthralgia, inability to walk, underlying disease: Legg-Calvé-Perthes disease	February; <1 week	IFA: <10	<1.1	pos, Ct 31.5	Sequencing/NGS: Whole CHIKV genome; CHIKV isolation
					February; >3 months (sample taken in May)	IFA:1280	4.9	ND	ND
	m	59	Thailand (Asia)	Fever, joint pain, light leucopenia and thrombocytopenia	March, <1 week	IFA: 160	5.1	pos, Ct 33.23	Sequencing and isolation not successful.
	f	24	Thailand (Asia)	NA	March, >3 months (sample taken in June)	IFA: >10 240	2.9	ND	ND
	m	31	NA	NA	NA; NA (sample taken in June)	IFA: >2560	7.3	neg	ND
	m	14	NA	NA	NA; NA (sample taken in July)	IFA: >2560	6.3	neg	ND
	f	51	Thailand (Asia)	NA	NA; NA (sample taken in July)	IFA: >2560	2.1	neg	ND

NA, not available; m, male; f, female; Total Ab HI, total antibody titer defined by hemagglutination inhibition test; IFA, immunofluorescence assay; pos, positive; neg, negative; Ct, cyclic threshold; NGS, next-generation sequencing; ND, not determined; ICU, intensive care unit; PNS, paraneoplastic neurologic syndromes.

Figure 1. Annual variation of serodiagnosed acute CHIKV infections in Finland, years 2009–2019.

Table 2. Primers and probes used in CHIKV RT-qPCR assay.

Primer/probe	Sequence (direction 5´→ 3´); gene area: nsP2 protein (product size 101 bp), location in CHIKV genome (GenBank ID: MH670649.1; NCBI), match (%)
CHIKV-F	GAG CAT ACG GTT ACG CAG ATA G^a; 3859–3880, 100%
CHIKV-R1	TAC TGG TGA TAC ATG GTG GTT TC^a; 3960–3938, 100%
CHIKV-R2	TGC TGG TGA CAC ATG GTG GTT TC^a; 3960–3938, 87%
CHIKV-Probe1	FAM-AAT CTG CGT ACT GGG ACG T-MGBNFQ^b; 3896–3914, 100%
CHIKV-Probe2	FAM-CTG CGT ATT GGG ACG CA -MGBNFQ^b; 3899–3915, 78%

CHIKV, chikungunya virus; bp, base pair; F, forward; R, reverse; nsP2, nonstructural protein 2; ID, identification code; NCBI, National Center for Biotechnology Information, U.S. National Library of Medicine.

^aAdapted from 19

^bDesigned in this study.

Figure 2. A phylogenetic tree of complete CHIKV coding sequences detected during 2009–2019. (a) All complete CHIKV coding sequences acquired from GenBank. 2(b) CHIKV strains from Thailand clustered within ECSA-lineage (c) CHIKV strain from Jamaica clustered within the Asian lineage.

A phylogenetic tree was constructed using the Bayesian Markov chain Monte Carlo (MCMC) method, implemented in Mr Bayes version 3.2 using a GTR-G-I model of substitution with 2 independent runs and 4 chains per run.

Table 3. Cycle threshold values of two different CHIKV dilution series using the nsP2 CHIKV RT-qPCR.

Virus	Dilutions tested, 10-fold	No of posit (x/5 parallel tests)	Median Ct value	SD	CV%
CHIKV Caribbean	10^−5	5/5	25.29	0.19	0.5%
	10^−6	5/5	29.95	0.08	0.3%
	10^−7	5/5	33.53	0.27	0.8%
	10^−8	1/5	35.14	ND	ND
CHIKV Ross	10^−5	5/5	26.74	0.12	0.5%
	10^−6	5/5	28.65	0.22	0.8%
	10^−7	5/5	31.62	0.20	0.6%
	10^−8	5/5	36.50	0.35	1.0%

CHIKV, chikungunya virus; posit, positives; ND, not determined; Ct, cycle threshold value; SD, standard deviation; CV, coefficient variation.

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