Globalized migration and transnational epidemiology

Today, in the 21st century, travel by millions of travellers (migrants and others) is far easier than in the 1800s. In the case of migrants, the widespread accessibility to means of travel and the availability of new technologies for staying connected to home and community of origin has resulted in transnational communities. Although members of these communities may be physically present in only one, they often 'live' in two places. Connections via communication technologies also are rein- forced in some cases through the rapid transport of food from home to the new community. This form of migration which can be thought of as transnational or globalized migration, is now revealing new connections between migration and epidemiology. This photo- essay concerns the importance of transnational migration to epidemiology by way of example—through words and pictures of an ongoing investigation into the sources of lead poisoning in a community of migrants (and immigrants) in Seaside, California originally from central Oaxaca, Mexico. The study began as a local investigation into sources of lead poisoning among children of immigrants who were routinely screened for lead in a small community clinic in California. Whereas the most likely source of lead was thought to be the ongoing use of lead-glazed ceramics among migrants from Mexico (a classic example of an apparent isolated practice/risk factor among a migrant community), the source was found to be related to contamination of foods in Mexico that was inadvertently transported to California through an ingeneous transnational migration practice that is increasing in popularity world-wide. The practice, called 'envios' (Spanish for send or transport) involves the frequent transport of prepared foods from Mexico to California. Envios in fact are 'mom and pop' express air transport businesses in which foods are sent from home in Oaxaca to home in California, often on a daily basis. Unfortunately, it was discovered that some of the foods contained lead. The as yet unidentified sources of the lead are currently undergoing investigation.3