Volume 19, Number 6—June 2013
Research
Effect of Travel on Influenza Epidemiology
Sanne-Meike Belderok
, Guus F. Rimmelzwaan, Anneke van den Hoek, and Gerard J.B. Sonder
, Guus F. Rimmelzwaan, Anneke van den Hoek, and Gerard J.B. Sonder
Table 1
Infection with >1 influenza type in 1,190 travelers from the Netherlands to (sub)tropical countries, October 2006–October 2007*
| Characteristic | Travelers at risk, no. (%) | Travelers with infection† |
Person-months of travel | IR, %‡ (95% CI) | Univariable analysis |
Multivariable analysis |
||||
|---|---|---|---|---|---|---|---|---|---|---|
| No. | AR, % (95% CI) | IRR (95% CI) | p value | IRR (95% CI) | p value | |||||
| All | 1,190 (100) | 86 | 7.2 (5.9–8.8) | 969 | 8.9 (7.1–10.9) | |||||
| Sex | ||||||||||
| M | 510 (43) | 31 | 6.1 (4.2–8.4) | 404 | 7.7 (5.3–10.8) | 1.0 | 0.286 | |||
| F | 680 (57) | 55 | 8.1 (6.2–10.4) | 565 | 9.7 (7.4–12.6) | 1.3 (0.8–2.0) | ||||
| Age group, y | ||||||||||
| <25 | 140 (12) | 8 | 5.7 (2.7–10.6) | 151 | 5.3 (2.5–10.1) | 1.00 | 0.098 | 1.0 | ||
| 25–34 | 381 (32) | 22 | 5.8 (3.8–8.5) | 315 | 7.0 (4.5–10.4) | 1.3 (0.6–3.0) | 1.3 (0.6–2.9) | 0.558 | ||
| 35–44 | 223 (19) | 21 | 9.4 (6.1–13.8) | 168 | 12.5 (7.9–18.8) | 2.4 (1.0–5.3) | 2.2 (1.0–4.9) | 0.063 | ||
| 45–54 | 226 (19) | 13 | 5.8 (3.2–9.4) | 165 | 7.9 (4.4–13.1) | 1.5 (0.6–3.6) | 1.3 (0.5–3.2) | 0.538 | ||
| 55–64 | 165 (14) | 17 | 10.3 (6.3–15.7) | 124 | 13.7 (8.3–21.5) | 2.6 (1.1–6.0) | 2.6 (1.1–6.1) | 0.025 | ||
| >65 | 55 (5) | 5 | 9.1 (3.4–19.0) | 46 | 10.9 (4.0–24.1) | 2.1 (0.7–6.3) | 1.9 (0.6–5.8) | 0.259 | ||
| Region of birth | ||||||||||
| Western | 1,103 (93) | 72 | 6.5 (5.2–8.1) | 905 | 8.0 (6.3–10.0) | 1.0 | 0.006 | 1.0 | ||
| Nonwestern | ||||||||||
| Africa | 12 (1) | 3 | 25.0 (6.8–54.1) | 11 | 27.3 (6.9–74.2) | 3.4 (1.1–10.8) | 3.7 (1.2–11.9) | 0.029 | ||
| Latin America | 47 (4) | 9 | 19.1 (9.8–32.2) | 31 | 29.0 (14.2–53.3) | 3.7 (1.8–7.4) | 3.8 (1.9–7.8) | <0.001 | ||
| Asia | 28 (2) | 2 | 7.1 (1.2–21.7) | 22 | 9.1 (1.5–30.0) | 1.1 (0.3–4.6) | 1.1 (0.3–4.4) | 0.926 | ||
| Previous travel to(sub)tropical country | ||||||||||
| Never | 224 (19) | 11 | 4.9 (2.6–8.4) | 180 | 6.1 (3.2–10.6) | 1.0 | 0.140 | |||
| 1–5 times | 687 (58) | 49 | 7.1 (5.4–9.2) | 573 | 8.6 (6.4–11.2) | 1.4 (0.7–2.7) | ||||
| >6 times | 279 (23) | 26 | 9.3 (6.3–13.2) | 217 | 12.0 (8.0–17.3) | 2.0 (1.0–4.0) | ||||
| Primary purpose of travel | ||||||||||
| Tourism | 1,017 (85) | 73 | 7.2 (5.7–8.9) | 826 | 8.8 (7.0–11.1) | 1.0 | 1.000 | |||
| Work or education | 100 (8) | 8 | 8 (3.8–14.6) | 86 | 9.3 (4.3–17.7) | 1.1 (0.5–2.2) | ||||
| Visiting friends and/or relatives | 73 (6) | 5 | 6.9 (2.6–14.5) | 57 | 8.8 (3.2–19.4) | 1.0 (0.4–2.4) | ||||
| Travel destination | ||||||||||
| Latin America | ||||||||||
| South America | 202 (17) | 13 | 6.4 (3.6–10.5) | 167 | 7.8 (4.3–13.0) | 1.0 | 0.373 | |||
| Central America and Caribbean | 120 (10) | 9 | 7.5 (3.7–13.3) | 78 | 11.5 (5.6–21.2) | 1.5 (0.7–3.5) | ||||
| Africa | ||||||||||
| Southern and Eastern Africa | 181 (15) | 12 | 6.6 (3.6–11) | 147 | 8.2 (4.4–13.9) | 1.1 (0.5–2.3) | ||||
| Middle, Western, Northern Africa | 110 (9) | 10 | 9.1 (4.7–15.6) | 75 | 13.3 (6.8–23.8) | 1.7 (0.8–3.9) | ||||
| Asia | ||||||||||
| Southeastern and Eastern Asia | 416 (35) | 25 | 6.0 (4.0–8.6) | 365 | 6.9 (4.5–10.0) | 0.9 (0.5–1.7) | ||||
| South-central and Western Asia | 125 (11) | 14 | 11.2 (6.5–17.7) | 97 | 14.4 (8.2–23.6) | 1.9 (0.9–4.0) | ||||
| More regions | 33 (3) | 3 | 9.1 (2.4–22.8) | 37 | 8.1 (2.1–22.1) | 1.1 (0.3–3.7) | ||||
| More continents | 3 (<1) | 0 | 0 | |||||||
| Symptoms | ||||||||||
| Fever | ||||||||||
| No | 1,073 (90) | 71 | 6.6 (5.2–8.2) | 854 | 8.3 (6.5–10.4) | 1.0 | 0.131 | |||
| Yes | 117 (10) | 15 | 12.8 (7.6–19.8) | 115 | 13.0 (7.6–21.0) | 1.6 (0.9–2.7) | ||||
| ILI§ | ||||||||||
| No | 1,150 (97) | 77 | 6.7 (5.4–8.3) | 930 | 8.3 (6.6–10.3) | 1.0 | 0.010 | 1.0 | 0.004 | |
| Yes | 40 (3) | 9 | 22.5 (11.6–37.3) | 38 | 23.7 (11.6–43.5) | 2.8 (1.4–5.7) | 2.8 (1.4–5.5) | |||
*AR, attack rate; IR, incidence rate; IRR, incidence rate ratio; ILI, influenza-like illness. Boldface indicates significance (p<0.05).
†Travelers with confirmed influenza infection for >1 influenza virus.
‡Per 100 person-months.
§Travelers with ILI are a subgroup of travelers with fever.
Page created: May 09, 2013
Page updated: May 09, 2013
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