The goal of this observational study is to learn how common infections are in intensive care units (ICUs) around the world and how they are treated. The study will look at all adults in the ICU during a single 24-hour period. The main questions it aims to answer are:

• What types of infections and antibiotic-resistant bacteria are most common in ICUs worldwide?
• How do resistance patterns affect how participants are treated and how they recover?

How are antibiotics used in ICUs, and how do hospitals practice antibiotic stewardship?

• What organ support treatments do participants with infections receive?
• What are the outcomes of participants with severe infections, including survival at hospital discharge (up to 60 days)?

Researchers will compare ICUs across regions and income levels to see how infection patterns, treatments, and outcomes differ around the world.

Participants will:

• Be counted if they are present in the ICU at any time during the study day.
• Have information collected from their medical record about their health, the infection they may have, treatments they receive, and their outcome at ICU and hospital discharge (up to 60 days).

Because this is an observational study, participants will not receive any new treatments as part of the study.

The Extended Prevalence of Infection in Intensive Care IV (EPIC IV) study is an international, multicenter, prospective 24-hour point-prevalence study designed to provide an updated global assessment of infection patterns, antimicrobial use, organ support strategies, and related outcomes among adult patients treated in intensive care units (ICUs).

This study follows the methodology of previous EPIC initiatives (1998, 2007, 2017), while addressing the substantial changes in infection epidemiology observed in the post-COVID-19 era, including shifts in microbial resistance profiles and ICU practice patterns. Each participating ICU will select a single study day within the predefined window, during which all patients aged ≥18 years who are present in the unit at any time during the 24-hour period will be included.

Data collection will be standardized across sites and will include:

• Patient-level information on demographics, comorbidities, admission characteristics, severity-of-illness scores (APACHE II, SAPS II, SOFA), organ dysfunction, microbiology results, antimicrobial therapies, and supportive treatments.
• Unit-level characteristics related to ICU organization, staffing, resource availability, and antimicrobial stewardship practices.
• Follow-up data on ICU and hospital outcomes, censored at 60 days after the study day.

No study-specific treatments or interventions will be administered. All clinical care will follow local practice. Microbiological testing and therapeutic decisions will not be influenced by the study protocol.

EPIC IV will enable detailed analyses of global and regional variability in infection epidemiology, antimicrobial resistance, antibiotic stewardship performance, and resource utilization. The large international sample size will support predefined sub-studies examining associations between infection type, resistance patterns, comorbidities, ICU structural characteristics, and patient outcomes. The dataset will also allow stratified analyses based on country income level and geographical region, generating evidence relevant to both high-income and low- and middle-income countries.

This coordinated effort aims to produce a comprehensive and contemporary description of infectious disease burden in ICUs worldwide and to inform future clinical guidelines, policy development, and resource allocation.

Inclusion Criteria:

• All adult patients (>18 years) treated in the participating ICUs on the study day.

Exclusion Criteria:

• Patients under 18 years

A worldwide sample of adult patients who are present in participating intensive care units during a single 24-hour study period, regardless of diagnosis, treatment, or reason for ICU admission.

The decision regarding the sharing of individual participant data has not yet been finalized. IPD availability will depend on ethical approvals, institutional policies, and data-governance requirements across participating sites.