CHICAGO — How is Helicobacter pylori transmitted in industrial countries with adequate sanitation?
Exposure to an infected person who is vomiting may be one way, according to findings from a large, 4-year study of California families with an index case of gastroenteritis.
The study found that the chance of acquiring H. pylori was 2.2 times higher when a person was exposed to a person with H. pylori infection who also had a case of infectious gastroenteritis than it was when a person lived with an H. pylori-infected individual who did not have infectious gastroenteritis.
The chance rose to 2.6 times if the H. pylori-infected person had vomiting with the gastroenteritis. Diarrhea also increased the risk, but only 2.0-fold, Sharon Perry, M.D., said at the annual Digestive Disease Week.
Figuring out how H. pylori is transmitted has been a “Holy Grail” of epidemiology for 20 years, said Dr. Perry, an epidemiologist at the Parsonnet Laboratory of the Division of Geographic Medicine and Infectious Diseases at Stanford University.
“This is not the Holy Grail study, but we may have visited the scene of the crime,” she said.
The study was conducted by contacting families in which an individual was seen for an episode of infectious gastroenteritis at any one of 15 clinics in the San Francisco Bay area. Of all the cases seen, 909 families agreed to participate in the study and were visited twice—first around the time of the gastroenteritis and again 3 months later. The family members were questioned, and stool and serology samples were collected.
Most of the families were Hispanic and lived in fairly crowded circumstances, Dr. Perry said.
Among 1,792 household contacts of a person with gastroenteritis, the study found 30 cases of individuals who were not infected with H. pylori at the first visit but were 3 months later, for an overall annualized rate of infection of 7%.
Seven of those new cases occurred in households without a person already infected with H. pylori, for an annualized rate of 4% for those households.
Thirteen new cases occurred in households were there was a person infected with H. pylori already, but that person was not the one who had infectious gastroenteritis, for an annualized infection rate of 7%. And 10 new cases occurred in households were a person infected with H. pylori initially was the same one who had infectious gastroenteritis, for an annualized infection rate of 11%, Dr. Perry said.
Half the new cases occurred in children less than 2 years of age.