Prevalence of H. pylori infection correlates best socio-economic status rather than race. In the United States, probability of being infected is greater for older persons (>50 years = >50%), minorities (African Americans 40-50%) and immigrants from developing countries (Latino > 60%, Eastern Europeans > 50%). The infection is less common in more affluent Caucasians ( < 40 years = 20%).
The green square represents the total population in the United States of uninfected (normal) persons within which is a circle representing the 30% who are infected (HP+). Persons in the infected group develop duodenal ulcer at the rate of about 1% per annum so that approximately one third eventually have peptic ulcer disease. The smaller circles represent diseases associated with H. pylori. Nearly all persons with duodenal ulcer are infected. Conversely, it is very unlikely that persons without H. pylori will ever develop duodenal ulcer. Gastric ulcer is usually caused by H. pylori, but about 30% of gastric ulcers in the United States occur in persons without H. pylori and can be related to aspirin and other non steroidal anti-inflammatory drugs (NSAIDs). Most gastric adenocarcinomas and lymphomas occur in persons with current or past infection with H. pylori. In developing countries the ulcer groups are smaller and the gastric cancer group may be larger. For example, in northern Brazil, gastric cancer is the most common malignancy in men.
In general, the following statements can be made to summarize prevalence of H. pylori in Western countries:
H. pylori affects about 20% of persons below the age of 40 years, and 50% of those above the age of 60 years.
H. pylori is uncommon in young children.
Low socio-economic status predicts H. pylori infection.
Immigration is responsible for isolated areas of high prevalence in some Western countries.
Studies of sera from epidemiologists and Californians show that a 50% decline in the prevalence of H. pylori has occurred in the United States since 1968.
In developing countries most adults are infected. Acquisition occurs in about 10% of children per annum between the ages of 2 and 8 years so that most are infected by their teens. It is evident from careful surveys that the majority of persons in the world are infected with H. pylori.
H. pylori can be cultured from the stools in most infected persons (using special techniques). This is evidence that spread by fecal oral contact with infected persons is likely. In addition, polymerase chain reaction (PCR) can detect H. pylori in dental plaque from 30% of persons with the gastric infection. This may be a less common source of transmission.