Hospital-Acquired Infections and Air Quality: Which Hospital Departments Will Be Most at Risk in 2026?

March 29, 2026

Healthcare-associated infections (HAIs) remain a significant public health challenge.
According to the latest national prevalence survey (ENP 2022) published by Santé publique France, 5.71% of hospitalized patients contracted an infection during their stay, a 14.7% increase compared to 2017, partly due to the COVID-19 pandemic. Excluding SARS-CoV-2 infections, this rate remains concerning at 5.35%, confirming a slight upward trend after a decade of progress.
The next ENP is scheduled for 2027.

Across Europe, the ECDC reports more than 3.5 million cases and over 90, 000 deaths annually in the EU. This situation calls for constant vigilance, particularly regarding indoor air quality in healthcare facilities—a factor that is often underestimated in the chain of transmission.

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The 3 departments most affected by healthcare-associated infections

Intensive care units: the highest risk

According to the 2022 ENP survey, with 23.17% of patients affected, the intensive care unit is the hospital department most at risk of healthcare-associated infections.
The reasons are structural: patients there are in critical condition and frequently undergo invasive procedures (intubation, mechanical ventilation, vascular catheters). These devices create numerous entry points for pathogens.

The most common infections in the intensive care unit are ventilator-associated pneumonia, catheter-related infections, and sepsis. The mortality rate for nosocomial sepsis in this unit can reach 52%.

From an air quality perspective, maintaining ISO 7 and ISO 8 zones, using HEPA filtration, and ensuring controlled air exchange are essential measures for limiting the ambient microbial load.

Operating rooms and intensive care units: perioperative contamination

Operating rooms and intensive care units are the primary settings for surgical site infections (SSIs), which are among the most common and serious types of infections. They can develop up to 30 days after surgery—or even up to a year in cases involving prostheses or implants.

Contamination can occur through airborne transmission (spores, bioaerosols), through direct contact during medical procedures, or via inadequately sterilized equipment. In these environments, air quality control is regulated: operating rooms must meet the requirements of ISO Class 5 to ISO Class 8, depending on the nature of the procedures.

Laminar flow ventilation systems and regular monitoring of particulate contamination can significantly reduce this risk.

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Geriatric care: particularly vulnerable patients

Older patients have weakened immune systems and numerous comorbidities. In geriatrics, the most common hospital-acquired infections are urinary tract infections (often associated with urinary catheters), respiratory infections, and aspiration pneumonia.

This department also handles a significant number of cases involving multidrug-resistant bacteria (MDRB), the prevalence of which is increasing as antibiotic use becomes more frequent. Indoor air quality and aerosol control play a key role here, especially since patients are often hospitalized for several weeks.

What role does air quality play in the transmission of healthcare-associated infections?

Pathogens are transmitted in healthcare facilities through two main routes:

direct contact (hands, surfaces, invasive medical devices)
airborne transmission, via droplets and aerosols

This second route of transmission is particularly dangerous in enclosed, crowded spaces.
As early as July 2020, the WHO confirmed that SARS-CoV-2 spreads primarily through aerosols smaller than 5 microns in diameter, which remain suspended in indoor air.
This finding also applies to other pathogens:

Mycobacterium tuberculosis (tuberculosis),
Aspergillus (aspergillosis),
Bordetella pertussis (whooping cough).

Aspergillosis: A Silent Threat

Caused by spores of the Aspergillus fungus, invasive aspergillosis primarily affects immunocompromised patients (organ transplant recipients, patients undergoing chemotherapy).
The spores circulate in the air and can colonize the lungs of patients with weakened immune systems.
High-efficiency filters and containment of high-risk areas are essential to prevent its spread.

Candidozyma auris: the new emerging fungal threat

Since 2024, a new fungus has emerged as a major concern for hospitals in France and across Europe: Candidozyma auris (formerly Candida auris).
Resistant to many antifungal drugs and capable of surviving for long periods on surfaces and medical devices, it causes invasive infections with mortality rates estimated between 29% and 53% depending on the study.
In Europe, 1,346 cases were reported across 18 EU countries in 2023 according to the ECDC, with a marked increase since 2020.

In France, 31 cases have been reported since January 2023, several of which formed an active cluster in 2025. In response to this risk, French health authorities implemented a recommendation in the summer of 2024 for systematic screening of all patients transferred from a foreign hospital.
A practical guide co-authored by the National Reference Center for Invasive Fungal Infections (CNR), the Hauts-de-France Regional Center for Infectious Diseases (CPias), and the French Society for Medical Mycology (SFMM) was published in May 2025.
This fungus primarily targets patients in intensive care units who are on invasive devices—once again highlighting the particular vulnerability of this department.

Tuberculosis and whooping cough: a worrying resurgence

Tuberculosis is on the rise in several European countries, driven by increasing antibiotic resistance and international travel.
Because it is transmitted through the air, healthcare facilities must maintain strict control over ventilation systems.

Whooping cough, meanwhile, has seen a resurgence in France since 2024, serving as a reminder that vaccine-induced immunity wanes over time.
In pediatric wards and maternity units, the risk of transmission between patients is high.

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Elderly people receiving care from medical staff

Post-COVID Assessment: What Lessons Can Be Learned for the Prevention of Healthcare-Associated Infections?

The COVID-19 pandemic has reshaped the landscape of healthcare-associated infections. As the leading cause of healthcare-associated infections in France as early as 2020, COVID-19 has highlighted the limitations of hospital infrastructure in dealing with airborne pathogens.

Factors contributing to transmission include a relaxation of preventive measures—particularly the removal of masks during breaks—as well as shared rooms and overcrowded wards. According to Santé publique France, this last factor is believed to have been responsible for 20% of hospital-acquired COVID-19 infections.

The health crisis has also exacerbated a pre-existing problem: antibiotic resistance.
In France, 130,000 patients per year are affected by infections caused by multi-drug or highly resistant bacteria, resulting in 5,500 deaths, according to data from the ECDC and Santé publique France.
The trend is worsening: antibiotic consumption increased by 5.4% in 2024 compared to 2023, with 27 million patients on prescriptions, representing 40% of the population.
The 2024 “One Health” summary from Santé publique France also notes a concerning resurgence in resistance to third-generation cephalosporins after years of slight decline. This overconsumption fuels the selection of resistant bacterial strains, making certain nosocomial infections increasingly difficult to treat.

What solutions are available to reduce the risk of airborne transmission?

The prevention of healthcare-associated infections relies on a set of complementary measures:

Hand hygiene

Hand hygiene is the first line of defense, and strict adherence to it remains the most effective measure for limiting transmission via the hands.

Management of Invasive Devices

Strict protocols for the insertion and care of catheters, tubes, and drains.

Institutional oversight

The REPIAS network (formerly RAISIN) provides national coordination, which is carried out locally by the CLINs and the Hospital Hygiene Operational Teams (EOHH).

Indoor air quality

Air purification serves as an additional preventive measure, particularly effective against airborne pathogens. HEPA filtration technologies capture submicron particles—bacteria, fungal spores, and viruses—where ventilation alone is insufficient.
Patient rooms, waiting rooms, common areas, and staff break rooms are all places where this approach can help reduce the viral and bacterial load in the air.

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Economic impact: a significant cost to the healthcare system

Hospital-acquired infections prolong hospital stays, lead to additional tests and treatments, and can result in long-term complications.
According to OPEPS data, the average additional cost per infection is estimated at between €3,500 and €8,000, totaling €2.4 to €6 billion per year in France.

A 10% reduction in the number of infections would result in savings of €240 million to €600 million—not to mention the considerable human benefit of preventing infections and deaths.

Healthcare-associated infections remain a major challenge for French and European healthcare facilities in 2026.
While improvements in hand hygiene and the management of invasive devices have led to real progress, airborne transmission remains a weak link—particularly in intensive care units, operating rooms, and geriatric units.

Incorporating indoor air quality into strategies for preventing infectious risks is no longer optional: it is a medical and economic necessity.
HEPA filtration, controlled ventilation, and monitoring of particulate contamination now form an indispensable trio for the safety of patients and healthcare workers.

Sources: Santé publique France (ENP 2022, One Health summary 2024), ECDC (C. auris report 2025), INSERM, WHO, Ministry of Health, OPEPS, Institut Pasteur / CNR on invasive fungal infections, SFMM, CPias.

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