Stroke is among the most common causes of death and persisting disability and 
therefore represents a great social and economic burden worldwide. In order to 
lower this burden it is essential to identify risk factors and respective 
preventive strategies. Besides the established stroke risk factors (e.g. 
hypertension, diabetes, hypercholesterolemia, atrial fibrillation) both acute 
and chronic infectious diseases have emerged as risk factors for stroke. Mainly 
acute respiratory tract infection but also urinary tract infections 
independently increase the risk of ischemic stroke. Such additional risk was 
shown to be highest for infection within 3 days before ischemia and the risk 
steadily declines with increasing time intervals between infection and stroke. 
Associations between stroke incidence and mortality and influenza epidemics have 
been demonstrated. Observational studies showed an inverse association between 
influenza vaccination and stroke risk; however, interventional studies in this 
field have not been performed so far. Chronic infections, presently discussed as 
stroke risk factors mainly include periodontitis and infections with 
Helicobacter pylori (Hp) and Chlamydia pneumoniae (Cp). Although most respective 
studies identified these infectious diseases as independent stroke risk factors 
interventional trials have not been performed so far and causality is not 
proven, yet. There is preliminary evidence that the number of pathogens to which 
a subject had been exposed to rather than single pathogens are associated with 
the risk of stroke or other cardiovascular diseases. Chronic infectious diseases 
are treatable conditions and their identification as causal contributors to 
stroke risk could offer new avenues in stroke prevention.