The purpose of this study is to assess the duration of immune responses in a group of 75 individuals 2-60 years of age presenting to the International Centre for Diarrhoeal Diseases Research, Bangladesh (ICDDR,B) admitted with acute cholera. Eighteen of these participants will be enrolled in a substudy of mucosal immunity involving duodenal biopsy. (Note that this protocol focuses exclusively on the subset of 18 study participants (healthy 18-45 [inclusive] year old non pregnant subjects) enrolled in the substudy of mucosal immunity involving duodenal biopsy. The remainder of the study is observational, involving collection of stool, vomit, and blood samples only [DMID protocol 06-0045]). A duodenal biopsy will be performed on enrollment or the next day and at Day 30. Nine of the 18 will undergo a third duodenal biopsy after 6 months of follow-up and 9 will undergo a third duodenal biopsy after 12 months follow-up. The objectives of this study are as follows: To measure immune responses directed against Vibrio cholerae antigens and evaluate the development of anti-V cholerae memory B cells in study participants with cholera. To assess the duration of the immune responses following an episode of cholera. To correlate the duration of antigen-specific, antibody-secreting cells for various cholera antigens in duodenal tissue with measurements of the duration of immunity based on antibody responses in serum, as well as circulating antigen-specific memory B cells. The study outcome measures will include: serum antibody responses to V cholerae Lipopolysaccharide (LPS), Cholera Toxin, B Subunit (CtxB), and Toxin-coregulated Pilus, Major Subunit (TcpA) on Days 2, 7, and 30 and at months 3, 6, 9, and 12 following enrollment; memory B cell responses to V cholerae LPS, ctxB, and TcpA on Days 2 and 30 and at months 3, 6, 9, and 12 following enrollment; and mucosal responses to V cholerae LPS, CtxB, and TcpA on Days 2 and 30 (in the 18 study participants) and at month 6 (9 study participants) and month 12 (9 study participants) following enrollment. This is a single site study with a 4 year duration requiring one year of patient participation.