Travel-associated illness trends and clusters, 2000-2010

Abstract

Longitudinal data examining travel-associated illness patterns are lacking. To address this need and determine trends and clusters in travel-related illness, we examined data for 2000-2010, prospectively collected for 42,223 ill travelers by 18 GeoSentinel sites. The most common destinations from which ill travelers returned were sub-Saharan Africa (26%), Southeast Asia (17%), south-central Asia (15%), and South America (10%). The proportion who traveled for tourism decreased significantly, and the proportion who traveled to visit friends and relatives increased. Among travelers returning from malaria-endemic regions, the proportionate morbidity (PM) for malaria decreased; in contrast, the PM trends for enteric fever and dengue (excluding a 2002 peak) increased. Case clustering was detected for malaria (Africa 2000, 2007), dengue (Thailand 2002, India 2003), and enteric fever (Nepal 2009). This multisite longitudinal analysis highlights the utility of sentinel surveillance of travelers for contributing information on disease activity trends and an evidence base for travel medicine recommendations.

Keywords: VFRs; case clusters; illness; surveillance; travel; trends; visiting friends and relatives.

Figure 1

GeoSentinel regions.

Figure 2

A) Reason for travel among 42,223 ill returned GeoSentinel patients, 2000–2010. Reason for travel missing for 188 (0.4%) patients. B) Destinations of travel among 42,223 ill returned GeoSentinel patients, 2000–2010. Region missing or unable to be determined (>1 region was visited) for 3,601 (8.5%) patients.

Figure 3

A) Proportionate morbidity (PM) for malaria (no. malaria cases/1,000 ill returned GeoSentinel patients) by region, 2000–2010. B) Absolute case numbers and proportionate morbidity for malaria (no. malaria cases/1,000 ill returned GeoSentinel patients) after travel to sub-Saharan Africa, 2000–2010. There were 1,363 total reported cases of malaria after travel to sub-Saharan Africa among the 18 GeoSentinel sites.

Figure 4

Proportionate morbidity (PM) for enteric fever (no. enteric fever cases/1,000 ill returned GeoSentinel patients) by region, 2000–2010.

Figure 5

Proportionate morbidity (PM) for dengue (no. dengue cases/1,000 returned GeoSentinel patients) by region, 2000–2010.

Figure 6

Proportionate morbidity (PM) (no. cases/1,000 returned GeoSentinel patients), 2000–2010. A) chikungunya, B) influenza, and C) rabies postexposure prophylaxis. Trends for chikungunya and influenza were not calculated because of substantial nonlinear year-to-year variation.

Figure 7

Regional results for malaria, enteric fever, and dengue. For malaria, the top region for acquisition was sub-Saharan Africa (77%), and the region with the top average proportionate morbidity (248/1,000 ill travelers) and the greatest trend (–39/1,000, p = 0.01) Oceania. For enteric fever, the top region for acquisition was south-central Asia (67%); regional trends were not assessed. For dengue, the top region for acquisition (50%) and the highest average proportionate morbidity and trend (+70.5/1,000, p = 0.004) was Southeast Asia.