Mitchell S. V. Elkind, from Columbia University (New York, USA) and colleagues studied a group of 1,625 stroke-free men and women, average age 68.4 years, living in a multiethnic urban community, following them for an eight-year period. The team found that five common infections -- Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus, and herpes simplex virus 1 and 2 -- were associated with increased stroke risk.  The infectious burden index was associated with an increased risk of stroke of 39% per standard deviation, after the researchers adjusted for confounding factors.  The team urges that: “A quantitative weighted index of infectious burden was associated with risk of first stroke in this cohort. Future studies are needed to confirm these findings and to further define optimal measures of infectious burden as a stroke risk factor.”