Figure 1. Risk factors for H. pylori-associated disease. Increased risk is associated with environmental factors such as a diet high in salt or low in iron, smoking, and the use of medications such as proton pump inhibitors and nonsteroidal anti-inflammatory drugs. H. pylori factors also play a role, with increased risk attributed to specific alleles of the vacA cytotoxin and the presence of the cag PAI, which encodes a type 4 secretion system (T4SS) and its effector, CagA. Host determinants of disease include the age of acquisition, gender, acid output following infection, an altered immune response due to genetic polymorphisms (IL-1β, IL-10, TNF-α, or IL-1RA), and perhaps the composition or structure of the microbial community.