Influenza in long-term Dutch travelers in the tropics: symptoms and infections

BMC Infectious Diseases

Table 1 Cross-tabulations of seroconversion for influenza viruses circulating worldwide during the study period for n = 602 long-term Dutch travelers, 2009 to 2012

Variables	Total respondents N	Seroconversion for any virus^a			A/California/007/09 H1N1pdm [H1pdm09]			A/Brisbane/59/07 [H1N1]			A/Brisbane/10/07 [H3N2]			A/Perth/16/09 [H3N2]			B/Florida/4/06			B/Brisbane/60/08
Variables	Total respondents N	n	n/N%	p value	n	n/N%	p value	n	n/N%	p value	n	n/N%	p value	n	n/N%	p value	n	n/N%	p value	n	n/N%	p value
Total	602	90	15	N/A	43	7	N/A	16	3	N/A	26	4	N/A	34	6	N/A	12	2	N/A	11	2	N/A
Age-group
<25 years of age	249	36	14		16	6		5	2		9	4		17	7		4	2		3	1
25–28 years	169	39	23		22	13		7	4		10	6		9	5		5	3		5	3
> = 29 years	184	15	8	<0.001^*	5	3	0.001^*	4	2	0.366	7	4	0.482	8	4	0.531	3	2	0.571	3	2	0.410
Gender
Female	389	63	16		31	8		12	3		17	4		24	6		5	1		5	1
Male	213	27	13	0.247	12	6	0.287	4	2	0.379	9	4	0.933	10	5	0.454	7	3	0.093	6	3	0.180
Major travel flu zone
Southeast Asia	252	39	15		16	6		3	1		11	4		17	7		5	2		5	2
Central & South America	222	36	16		20	9		10	5		9	4		10	5		5	2		5	2
Asia, other	21	2	10		1	5		0	0		0	0		0	0		1	5		0	0
Africa	107	13	12	0.687	6	6	0.580	3	3	0.132	6	6	0.702	7	7	0.469	1	1	0.679	1	1	0.771

Age was summarized into tertiles: <25 years, 25–28 years and > =29 years. N/A Not Applicable
^aIn 10 individuals where the pre-travel titre was ≥40 there was evidence of re-infection (4 fold rise in antibody titre)
P value throughout is Pearson’s chi-squared; Significance assigned (*) at p < 0.01

ISSN: 1471-2334