After the large outbreak in 2004, the CDC (2004) and the government of Kenya initiated a public health response that included hospital- based, clinical disease surveillance for acute aflatoxicosis in the four hospitals serving the high-risk districts (Makueni and Kitui). Cases were reported to public health officials by clini- cal care providers along with other reportable diseases. Because there is no diagnostic test for aflatoxicosis, cases were defined as acute hepatic inflammation of unknown etiology (where viral and other causes have been ruled out). In addition, the Kenyan government, along with the Food and Agriculture Organization (FAO), initiated a public education campaign on afla- toxin prevention. Finally, household maize sur- veys during the high-risk season (April–June) were initiated in Makueni and Kitui to under- stand the distribution of aflatoxin in maize and to guide urgent interventions to control afla- toxin exposure and prevent aflatoxicosis. This report presents an analysis of house- hold maize survey data collected in 2005, 2006, and 2007 as part of the urgent public health responses. The data were originally col- lected to guide and target maize replacement efforts and other interventions. The objec- tives of the present analysis were to describe the distribution and extent of maize aflatoxin contamination and to identify associated fac- tors, such as the source of the contaminated maize (i.e., maize homegrown on the farm where consumed, maize purchased from a store or market, or maize received as part of relief efforts), amount of maize produced, and aflatoxin awareness, among subsistence farmers living within the Makueni and Kitui districts of the Eastern Province of Kenya. Methods Study design. We conducted an analysis of data collected during the household maize sur- veys in 2005, 2006, and 2007. We employed a cross-sectional study design in all 3 years. The data set includes interview data collected at each household along with one or more house- hold maize samples for aflatoxin analysis. The surveys were conducted in Makueni and Kitui districts between April and June (high-risk season). Aflatoxicosis outbreaks were occur- ring in the region during the 2005 and 2006 surveys, but not during the 2007 survey. The 2005 and 2006 surveys included households systematically selected because one or more cases of aflatoxicosis resided in the household. These aflatoxicosis case households were iden- tified through the ongoing hospital-based, clinical disease surveillance described above. This study was approved by the Centers for Disease Control and Prevention Institutional Review Board. Sample selection. In 2005, 2006, and 2007, we conducted the maize household sur- veys in the divisions (geographic government units within districts) within Makueni and Kitui districts where cases of aflatoxicosis had occurred during the current outbreak or pre- vious outbreaks. Each year villages were ran- domly selected from these divisions. However, the methods used to obtain a random sample of villages and the number of villages selected varied slightly from year to year. These varia- tions reflect differences from year to year in capacity, available resources, and public health response needs. In 2005, we selected a total of 36 villages. We selected half (18) from a list of villages where a person with aflatoxicosis resided, as reported through hospital-based disease sur- veillance and obtained from the local pub- lic health officers. The other half (18) of the villages were randomly selected from the affected region but where no cases of aflatoxi- cosis were reported. Specifically, using census data, we randomly selected 18 sublocations (the smallest geographic government unit given in Kenya census data) from a list of sub- locations within the affected divisions. One village was selected from each sublocation. In 2006, we selected a total of 18 villages from 18 randomly selected sublocations within affected divisions without regard to whether an aflatoxicosis case resided in the village. In 2007, we selected a total of 24 villages with- out regard to whether a case resided in the village. The methods used to obtain a random sample differed in 2007 from 2005 and 2006. In 2007, we randomly selected points using a geographical information system (ArcMap® 9.0; ESRI, Redlands, CA, USA) random point generator within the affected divisions and selected a village based on proximity to a randomly selected point. In 2005, 2006, and 2007, we used the same method to select households within the selected villages. If a case resided in the village, the case household was included in the survey. To select the other (noncase) households in the village, we randomly chose a direction from the village center by spinning a pencil and walking in the direction of the pencil point, a method borrowed from the World Health Organization Expanded Program on Immunization (Lemeshow and Robinson 1985). In each year, we enrolled the maximum number of households that were logistically feasible to visit each day. Questionnaire. In all 3 years, we adminis- tered a standardized questionnaire to the head of household (18 years of age or older) after obtaining informed consent. We asked questions pertaining to the source of maize currently being eaten by members in the household. We defined the sources of maize as a) homegrown: maize grown on the household farm where it will be consumed; b) purchased: maize bought from local mar- ket vendors, which could be locally grown, Environmental Health Perspectives • volume 119 | number 12 | December 2011 Maize aflatoxin levels in eastern Kenya imported, or a blend of both; and c) relief: maize provided by the Kenyan government or a nongovernmental organization as part of relief efforts. We also asked about maize crop production and assessed the amount of home- grown maize produced from the current har- vest by asking household members to report the number of kilograms or number of 90-kg bags of maize produced during the current harvest and to report alternative food sources. We asked about awareness of aflatoxin con- tamination and aflatoxicosis through multiple questions about drying and storing practices and knowledge of the potential causes of jaun- dice. In addition, we asked about the health of family members, including questions about any current symptoms of jaundice among household members and other symptoms that could be attributed to aflatoxicosis. Maize collection. We attempted to col- lect at least one sample of maize from each selected household for analysis. In all 3 years, we sampled the maize being consumed by household members at the time of the study, regardless of source. Maize samples were classi- fied as homegrown, purchased, or relief maize. If a household had maize from more than one source, we requested a sample from each one. Most households store maize in 90-kg bags. We used a process recommended by the FAO for maize collection that has not been statisti- cally verified (Njapau 2008). Specifically, we took multiple samples from different parts of one bag and combined them to produce a rep- resentative 1-kg sample for analysis. If a house- hold had several bags from the same source, we collected grains from a random sample of bags to create the 1-kg sample. To reduce the risk of cross-contamination between house- holds, we collected maize samples using tools that were present at the household. We stored and transported samples for analysis in paper bags to control moisture content. We provided each household with a 2-kg bag of maize flour for their willingness to provide a sample. Maize aflatoxin analysis. We analyzed maize samples for aflatoxin levels at the National Public Health Laboratory in Nairobi, Kenya, using the immunoaffinity column (AflaTEST; VICAM, Milford, MA, USA) method 977.16 (Association of Official Analytical Chemists 2005) that was provided by VICAM. We mixed ground maize (50 g) that passed through a no. 20 sieve with 100 mL methanol:water mixture (80:20) and 5 g sodium chloride before filtration. We diluted 10 mL of the extract with 40 mL distilled water that was filtered again through a microfiber glass filter into a glass syringe. We then passed 2 mL of the twice- filtered mixture through the immunoaffinity column at a rate of 1–2 drops/sec. We washed the column with water and recovered the aflatoxins using 1 mL methanol. We read the methanol extract using a calibrated VICAM 1795