Epidemiology

Globally, the overall rate of healthcare-associated Clostridioides difficile infection has been reported to be 2.24 cases per 1000 admissions per year and 3.54 cases per 10,000 patient days per year. The rate in intensive care units and internal medicine wards was 11.08 and 10.8 cases per 1000 admissions per year, respectively. The rate for community-acquired infection is much lower (0.55 cases per 1000 admissions per year). Higher rates of infection have been reported in the US compared with Europe and the Western Pacific region.[4] An increasing proportion of infections treated by hospitals are community-acquired; however, the reason for this remains unclear.[5]

C difficile infection has become the most common cause of healthcare-associated infections in US hospitals, with estimates of 500,000 infections and 29,000 deaths (within 30 days of the initial diagnosis) among patients in the US in one year. Approximately 65% of cases were healthcare-associated (including nursing homes and patients who have visited outpatient settings), but only 24% of cases had onset while in hospital. The incidence of healthcare-associated infection was 92.8 per 100,000 persons, while the incidence of community-associated infection was 48.2 per 100,000 persons. White people, females, and patients aged 65 years and older had a higher incidence of infection.[6] In terms of patient-days, the incidence rates of hospital-onset infection were 8 and 2 cases per 10,000 patient-days for healthcare-associated and community-associated infection, respectively, in the US.[7]​ A prospective study found that C difficile infection accounted for approximately 10% of patients presenting to the emergency department with diarrhoea and no vomiting, and more than one third of these patients lacked traditional risk factors for infection.[8]

The epidemiology changed in the 2000s due to the emergence of the more toxic North American pulsed-field gel electrophoresis type 1 (NAP1) strain (also known as PCR ribotype 027 [RT027] epidemic strain).[9][10][11]​​ Outbreaks occurred in North America, the UK, Europe, and Asia. The NAP1 strain has been decreasing in prevalence since it was first isolated, but remains a significant problem in the US. The emergence of this strain may be the result of widespread use of fluoroquinolones.[12] The NAP1 strain is more prevalent in healthcare-associated infections.[6]​ Ribotype 106 (RT106) is found globally, and became more prevalent in the 2010s (it became the most prevalent strain in the US in 2016). It is thought to cause less severe disease compared with RT027.[13]

Recurrence rates have been reported to vary from 5% to 50%, although one study found at least one recurrence in 21% of healthcare-associated infections and 14% of community-associated infections.[6] The risk of developing a first recurrent episode after an initial episode is 25%, with a risk of 38% for a second, 29% for a third, and 27% of a fourth episode. The risk of severe infection decreased with each subsequent recurrence.[14] The annual incidence of multiply-recurrent infection has increased in recent years. Risk factors for recurrent infection include female sex, increasing age, chronic kidney disease, diagnosis in a nursing home, healthcare-associated infection, prior hospitalisation, previous recurrent infection, and recent use of corticosteroids or proton-pump inhibitors.[15][16] Patients on acid-suppressing drugs were 64% more likely to develop recurrent C difficile infection compared to patients not on acid-suppressing drugs, and the association was greater with PPIs.​​​[17]

In the UK, approximately 20,000 cases were reported between November 2023 to November 2024 (trust-apportioned cases only).[18]​ Approximately 86,000 cases were reported in 26 countries across Europe in 2018-2020, approximately 61% of which were healthcare associated.[19] In terms of patient-days, the incidence rates of hospital-onset infection were highest in Poland (6.2 and 1.4 cases per 10,000 patient-days for healthcare-associated and community-associated infection, respectively) and lowest in the UK (2 and 0.6 cases per 10,000 patient-days for healthcare-associated and community-associated infection, respectively).[7]​​ Incidence rates in Asia are reported to be similar to rates in Europe and North America.[20]

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