Hospital-acquired infections are claiming more American lives each year than AIDS, breast cancer, or automobile accidents. The right physical environment, including single-patient rooms; well-designed ventilation systems and air filters; easy-to-clean, nonporous surface materials; and plenty of sinks for washing hands; could reduce the spread of infection, architects say. They even have research supporting the concept, and now hospitals across the country are using this information to reduce infections from the ground up.