Severe sepsis is a major cause of death in the United States, particularly among critically ill patients in non-coronary intensive care units (ICUs). It is often caused by respiratory tract infections, especially pneumonia, which is associated with high mortality. The type of organism causing sepsis significantly affects outcomes, with gram-positive organisms now more common than gram-negative infections. Recent studies show that acute infections can worsen pre-existing chronic conditions or lead to new ones, resulting in poor long-term outcomes for survivors. Older age, male gender, black race, and preexisting chronic health conditions are risk factors for severe sepsis, suggesting that prevention strategies should target these vulnerable groups. Sepsis and severe sepsis are major public health issues, with high hospital costs and significant mortality rates. The article discusses the epidemiology of severe sepsis, including common causes, risk factors, and long-term outcomes, with a focus on developed countries. Definitions of sepsis and severe sepsis have evolved, with the 1991 and 2001 consensus conferences providing frameworks for diagnosis. However, these definitions have limitations, and the use of administrative data sets for epidemiological studies can be imprecise. The incidence of severe sepsis in the US is estimated at 300 cases per 100,000 population, with about half occurring outside the ICU. Mortality rates remain high, especially in septic shock. The epidemiology of sepsis is complex, influenced by factors such as age, gender, race, and underlying health conditions. The article also highlights the importance of understanding the etiology of infections, the role of antibiotic resistance, and the impact of environmental factors. Long-term outcomes for sepsis survivors include increased mortality and chronic health issues, emphasizing the need for better prevention and treatment strategies.Severe sepsis is a major cause of death in the United States, particularly among critically ill patients in non-coronary intensive care units (ICUs). It is often caused by respiratory tract infections, especially pneumonia, which is associated with high mortality. The type of organism causing sepsis significantly affects outcomes, with gram-positive organisms now more common than gram-negative infections. Recent studies show that acute infections can worsen pre-existing chronic conditions or lead to new ones, resulting in poor long-term outcomes for survivors. Older age, male gender, black race, and preexisting chronic health conditions are risk factors for severe sepsis, suggesting that prevention strategies should target these vulnerable groups. Sepsis and severe sepsis are major public health issues, with high hospital costs and significant mortality rates. The article discusses the epidemiology of severe sepsis, including common causes, risk factors, and long-term outcomes, with a focus on developed countries. Definitions of sepsis and severe sepsis have evolved, with the 1991 and 2001 consensus conferences providing frameworks for diagnosis. However, these definitions have limitations, and the use of administrative data sets for epidemiological studies can be imprecise. The incidence of severe sepsis in the US is estimated at 300 cases per 100,000 population, with about half occurring outside the ICU. Mortality rates remain high, especially in septic shock. The epidemiology of sepsis is complex, influenced by factors such as age, gender, race, and underlying health conditions. The article also highlights the importance of understanding the etiology of infections, the role of antibiotic resistance, and the impact of environmental factors. Long-term outcomes for sepsis survivors include increased mortality and chronic health issues, emphasizing the need for better prevention and treatment strategies.