According to a report of British researchers, infections may lead to deep vein thrombosis, an illness which causes blood clots to form, usually in the leg and which can eventually cause a heart attack. Infection is also associated with pulmonary embolism, in which the blood clots travel to the lungs. Dr. Liam Smeeth from the London School of Hygiene and Tropical Medicine and his colleagues analyzed the data received from 7,278 deep vein thrombosis patients and 3,755 pulmonary embolism patients registered in the U.K. database. The study showed that the people who had suffered from respiratory or urinary infections are almost twice as likely to develop blood clots after two weeks, caused by inflammation in the blood vessel. They needed more than 1 year to return to normal.Deep vein thrombosis is an affection which contributes to around 10% of deaths among hospital patients each year. The clots occur in the leg veins, but may also reach the lungs. The presence of blood clots in the lungs, also called pulmonary embolism, is fatal in more than 30% cases if not treated. "We suspect that infections cause an inflammatory effect on the lining of the blood vessel wall - or endothelium. But the blood clots could equally be caused because as people are ill and go to bed staying still for longer," said Dr. Smeeth, member of the research team. The researchers concluded: "Our finding that two infectious processes in different organ systems are associated with a substantial, reversible increase in the risk of venous thromboembolism suggest that acute infections may have a causal role in triggering events."