<prompt> Which of the following patient is most likely to harbor a Helicobacter pylori infection in the stomach?A 60-year-old middle-income AmericanA 25-year-old American in a low-income groupA 25-year-old ZairianA 60-year-old Pakistani  <response>: The most important risk factors for H. pylori infection include older age, low income, and residence in a developing country. It is believed that infection generally is acquired in childhood. Although humans are the major reservoir of H. pylori, the route of infection is unclear, with fecal-oral and oral-oral spread both being possible. H. pylori is endemic in only 30 of Americans, but prevalence rates are as high as 80 in developing countries. Infection with a related species, H. heilmanii, is about 1 as common as H. pylori infection. 