WS/T 857-2025 in English

Background and Significance of the Standard

WS/T 857-2025, "Criteria for Determining Hospital-acquired Infections: General Principles," was issued by the National Health Commission on July 30, 2025, and will officially come into effect on February 1, 2026. This standard, jointly drafted by leading domestic medical institutions including Xiangya Hospital of Central South University and Peking Union Medical College Hospital of the Chinese Academy of Medical Sciences, marks a new, more standardized phase in hospital infection control in my country.

As a recommended health industry standard, this standard applies to all types of medical institutions at all levels, providing unified technical specifications and operational guidelines for the determination of hospital-acquired infections. It is worth noting that this standard explicitly does not apply to the diagnosis and treatment of clinical infection cases; it is intended to serve as a basis for determination by infection control professionals.

Analysis of Core Terminology Definitions

This standard provides precise definitions of key terms, laying a theoretical foundation for identification:

Deepening the Definition of Nosocomial Infection

Nosocomial infection is defined as "infection caused by the transmission of pathogens during medical services." This definition emphasizes the medical relevance of infection and highlights the key aspects of prevention and control.

Definition of Pathogens

The standard clearly divides pathogens into two categories: microorganisms and parasites. Microorganisms include prions, viruses, chlamydia, rickettsiae, mycoplasmas, bacteria, fungi, and spirochetes; parasites include protozoa, helminths, and medical arthropods. This classification provides a complete framework for tracing the source of infection.

Reinfection Time Window Concept

The innovative concept of the reinfection time window is proposed, defined as "14 days after the first occurrence of a hospital infection that meets the criteria." Reinfections of the same type within this time window are not counted as new infections. This rule avoids duplicate counting and improves data accuracy.

Distinguishing between Colonization and Infection

Clarifying that colonization refers to "the growth of bacteria and other microorganisms in a patient's skin, gastrointestinal tract, respiratory tract, oral cavity, genital tract, and other areas, but without the development of clinical manifestations of infection." This distinction is crucial for avoiding overdiagnosis.

Analysis of the Judgment Principle System

The standard has established a complete judgment principle system, covering multiple dimensions:

Comprehensive diagnosis principle

The standard emphasizes that diagnosis should be based on a comprehensive combination of clinical manifestations, epidemiological data, imaging, laboratory test results, and other clinical data, reflecting the multidimensional nature of modern medical diagnosis. This principle requires infection control personnel to possess comprehensive medical knowledge and be able to integrate various information to make accurate judgments.

Principle of Exclusion

It explicitly requires the exclusion of corresponding symptoms, signs, imaging changes, and laboratory test results caused by non-infectious diseases, as well as infections already present at the time of admission and infections in the incubation period. The establishment of these exclusion criteria effectively avoids the misdiagnosis of community-acquired infections as hospital-acquired infections.

Detailed Interpretation of Judgment Basis

Article 5 of the standard clarifies the specific judgment basis, forming a complete logical system:

Time Judgment Criteria

For infections with a clear incubation period, the judgment standard is exceeding the average incubation period; for infections without a clear incubation period, the time node is 48 hours after admission. The setting of this time standard is based on the general laws of infection development and has sufficient scientific basis.

Association Determination

The standard stipulates that "the current infection is directly related to the previous hospitalization" should be classified as a nosocomial infection. This provision reflects consideration of the long-term impact of medical practices and expands the timeframe for nosocomial infections.

Site Extension Determination

"The development of a new infection at a new site beyond the original site of infection" should be classified as a nosocomial infection, but migratory lesions of sepsis and complications of the original infection must be excluded. This provision requires accurate distinction between spread of infection and new infections.

Assessment of Special Populations

Special provisions are made for neonatal infections, clarifying that infections acquired through the birth canal or placenta must be determined based on the time of infection, and infections occurring more than 48 hours after hospitalization are classified as nosocomial infections.

Protection of Medical Staff

Clarifying that "infections acquired by hospital staff while working in the hospital should be classified as nosocomial infections" demonstrates the importance attached to the occupational protection of medical staff.

In-depth analysis of exclusion basis

Article 6 of the standard systematically stipulates the circumstances for excluding hospital infection, forming an important negative judgment criterion:

Application of the superinfection time window

The introduction of the concept of the superinfection time window is a key innovation of this standard. Within 14 days of the initial infection, infections at the same site with the same pathogen or with different pathogens at the same site are no longer counted as new infections. This provision is based on the pathophysiological characteristics of infection and avoids double counting of infections at different stages of the same infection process.

Exclusion of special pathogens

The standard explicitly lists infections caused by pathogens such as Blastomyces, Histoplasma, Coccidioides, Paracoccidioides, Cryptococcus, and Pneumocystis as generally not considered nosocomial infections, primarily because these pathogens have long incubation periods and are often community-acquired. However, the standard also provides for exceptions—"unless there is a strong indication of hospital infection caused by the pathogen," reflecting a combination of principle and flexibility.

Definition of Latent Infection Activation

Explicitly excludes infections such as herpes zoster virus infection, herpes simplex virus infection, syphilis, and tuberculosis from hospital infection due to latent infection activation caused by decreased immune function. This provision accurately distinguishes the time difference between infection acquisition and onset.

Nosocomial Infection Classification System

Appendix A provides the classification and names of nosocomial infections in the form of a normative appendix, establishing a complete classification framework:

Systematic Classification Structure

The standard divides nosocomial infections into 12 major categories based on anatomical systems, including urinary tract infections, surgical site infections, bloodstream infections, respiratory tract infections, bone and joint infections, central nervous system infections, cardiovascular system infections, eye, ear, nose, throat, and oral infections, digestive system infections, reproductive system infections, skin and soft tissue infections, and systemic infections. Each major category is further subdivided into specific infection types.

Specific Infection Name Standards

Standardized names are given for each infection, such as "urinary tract infection (catheter-related or non-catheter-related)" and "superficial incisional infection (major superficial incisional infection, minor superficial incisional infection)," laying the foundation for unified terminology.

Device-Related Infection Identification

Specially identifies device-related infections, such as "laboratory-confirmed central venous catheter-related bloodstream infection" and "pneumonia (ventilator-related, post-operative pneumonia, unrelated to the ventilator or surgery)," highlighting the crucial role of medical devices in the development of infections.

Implementation Recommendations and Operational Guidelines

Implementation Pathways for Medical Institutions

Medical institutions at all levels should establish a workflow for determining hospital-acquired infections (HAIs) based on this standard, including: case discovery, information collection, comprehensive analysis, determination and decision-making, and record-keeping and reporting. It is recommended that a dedicated determination team be established, comprised of infection control physicians, clinicians, and microbiology personnel.

Timing and Frequency of Determination

The standard requires that "clinical physicians and hospital infection control professionals should collaborate to promptly determine HAIs." A daily screening and timely determination model is recommended to ensure that determinations are made promptly after an infection occurs.

Documentation requirements

All determination processes should be fully recorded, including the basis for determination, reasons for exclusion, participants and other information. It is recommended to establish an electronic determination system to achieve structured storage and analysis of data.

Quality control measures

Establish a quality control mechanism for determinations, including regular review, cross-validation, expert review, etc., to ensure the consistency and accuracy of determinations. It is recommended to conduct a sampling review of determined cases every quarter, and control the error rate within 5%.

Training and education program

Carry out systematic standard training for clinical physicians and infection control personnel, focusing on the principles, basis and exclusion conditions for determination, and improving practical operation capabilities through case teaching. It is recommended to conduct full-staff training at least once a year.

Technological Evolution and Standard Innovation

Conceptual System Innovation

This standard systematically introduces concepts such as nosocomial infection and re-infection time window into health industry standards for the first time, enriching the theoretical basis for hospital infection control and providing conceptual tools for accurate judgment.

Decision Logic Optimization

A more complete decision logic system has been established, with both positive judgment basis and negative exclusion conditions, forming a complete decision closed loop and reducing the arbitrariness of subjective judgment.

Improvement of the Classification System

The classification system established in Appendix A is comprehensive and has clear levels. It provides a unified framework for the standardized collection and analysis of hospital infection monitoring data, facilitating the comparison and exchange of data between different medical institutions.

Coordination with relevant standards

This standard is coordinated with relevant standards such as WS/T 312 "Nosocomial Infection Monitoring Specification" and GB 15982 "Hospital Disinfection and Hygiene Standard", and together they constitute a standardized system for nosocomial infection control.

The implementation of WS/T 857-2025 will significantly improve the standardization level of nosocomial infection case assessment in my country, provide strong technical support for nosocomial infection prevention and control work, and ultimately achieve the goal of ensuring patient safety and medical quality.