The 2025–2026 influenza season has reached severity levels not observed in years. According to the U.S. Centers for Disease Control and Prevention (CDC), at least 11 million illnesses, 120,000 hospitalizations, and more than 5,000 deaths have occurred to date, with influenza activity expected to continue rising in many regions of the United States.¹

Much of the current surge is being driven by Influenza A (H3N2), a contagious respiratory virus, including a genetically distinct subclade often referred to in the media as “Super K.” But beyond variants and headlines lies a more fundamental and still widely misunderstood issue:

Ventilation and surface cleaning alone won’t stop an airborne, respiratory virus.

Surface contamination and close contact can contribute to transmission. Hand hygiene, environmental surface disinfection, distancing, and isolation protocols remain important components of infection prevention.

However, a substantial body of scientific evidence now shows that airborne transmission through aerosolized particles is a dominant pathway for many respiratory infections in indoor environments.^2–5

This understanding is reflected in guidance from the CDC, the World Health Organization (WHO), and ASHRAE, all of which recognize inhalation of infectious aerosols as a critical factor in enclosed spaces.^4,5

Another common misunderstanding in infection control is confusion between droplets, aerosolized particles, and the term “airborne.” When people breathe, speak, cough, or sneeze, they release respiratory particles across a wide size range:^2,3

• Large droplets are relatively heavy and fall quickly to the ground due to gravity, typically within seconds and within a short distance.
• Smaller particles, often called aerosolized particles or droplet nuclei (generally less than ~5 micrometers), behave very differently.

Once particles are small enough, gravity no longer removes them on a meaningful infection-control timescale. Instead, they remain suspended and move with airflow, making them readily inhalable by others sharing the same indoor air—often before ventilation, filtration, or dilution can reduce exposure.^2–4

These aerosolized particles:

• Do not settle immediately
• Are generated by normal breathing, not just coughing or sneezing
• Bypass the nose and throat’s natural filtering defenses
• Penetrate deep into the lungs^2,3

These aerosolized particles are what make respiratory viruses airborne indoors.

Ventilation is essential for indoor air quality. Increasing outdoor air, improving airflow patterns, and meeting ventilation standards all reduce average exposure over time.

But ventilation operates on time.

Air exchange follows exponential decay, meaning contaminants are diluted gradually over minutes—not removed instantaneously.^4,6 Even in buildings with excellent ventilation, high air-change rates, or 100% outside air, there is an unavoidable time gap between:

1. When aerosolized pathogens are released, and
2. When ventilation removes or sufficiently dilutes them

Infection can occur during that gap.^4,6

This is not a failure of ventilation design. It is a fundamental physical limitation of ventilation as an infection-control mechanism. Ventilation reduces risk over time, but it does not prevent near-field exposure in the moments immediately following pathogen release.^4,6

High-efficiency filtration and surface disinfection remain important parts of a layered infection-control strategy—but each has intrinsic limitations:

• Filters capture particles; they do not inactivate pathogens
• MERV-13 and MERV-14 filters capture a fraction of sub-micron aerosols but do not reliably remove all respirable particles⁷
• Effectiveness depends on airflow, installation quality, maintenance, and avoidance of bypass
• Even high-efficiency filtration does not address pathogens already present in the breathing zone before air reaches the filter

High-efficiency particulate air (HEPA) filtration can be effective but often requires major system modifications and is not practical for many existing buildings.⁷

Surface disinfection addresses what has already settled. It does not address aerosolized pathogens suspended in the air people are actively breathing.

Moving air and trapping particles are not the same as neutralizing infectious agents.

Germicidal ultraviolet (GUV), also referred to as upper-room UVGI or upper-air UV, is an engineering control specifically designed to interrupt airborne transmission of contagious respiratory viruses and bacteria in occupied indoor spaces.

Unlike ventilation or filtration, upper-room GUV:

• Acts within the occupied space
• Operates continuously while people are present
• Inactivates pathogens as air circulates, rather than waiting for air changes

GUV uses UV-C light to damage viral and bacterial nucleic acids, preventing replication and rendering pathogens non-viable.^8,9 Properly designed systems confine UV-C energy to the upper portion of the room through optical design and shielding, keeping occupant exposure well below established safety limits set by CDC and NIOSH.^8,9

Upper-room GUV has been studied and applied for more than 100 years, beginning with measles control in schools in the 1930s and later expanding to tuberculosis, influenza, and other airborne diseases.¹⁰

Modern guidance from CDC, NIOSH, and ASHRAE recognizes upper-room GUV as an effective layered control for airborne infection risk, particularly where ventilation alone cannot act quickly enough.^4,8

Importantly, peer-reviewed field evidence exists. A multi-year study published in the Journal of the American Veterinary Medical Association (JAVMA) documented an 87% reduction in upper respiratory infections following installation of upper-room GUV systems in an occupied congregate environment.¹¹ While conducted outside of human healthcare, the aerosol physics and UV inactivation mechanisms are species-independent.

Since 2008, Aerapy has focused exclusively on indoor air disinfection, engineering systems designed to reduce viable airborne pathogen load in occupied indoor environments.

Today, Aerapy systems operate in more than 1,000 healthcare, government, and congregate environments nationwide. These systems employ patented upper-room germicidal ultraviolet (GUV) technology that operates both passively using natural convection and actively, through integrated airflow that draws air into the upper disinfection zone. All systems are independently certified and tested safe for continuous operation in occupied spaces by nationally recognized testing laboratories, and are designed in accordance with published CDC and NIOSH guidance.

Current infection-control strategies appropriately include:

• Vaccination
• Hand hygiene and surface disinfection
• Ventilation optimization
• Filtration
• Respiratory protection where appropriate

All are necessary, and each addresses a specific transmission pathway. But none of these strategies alone or in combination directly inactivates aerosolized pathogens in the breathing zone before they are inhaled.^4,6

Aerapy’s germicidal ultraviolet (GUV) technology covers that gap.

1. CDC. FluView: Weekly U.S. Influenza Surveillance Report. (URL)
2. Bourouiba L. Turbulent gas clouds and respiratory pathogen emissions. JAMA. 2020. (URL)
3. Milton DK et al. Influenza virus aerosols in human exhaled breath. PLoS Pathogens. 2013. (URL)
4. ASHRAE. Position Document on Infectious Aerosols. (URL)
5. WHO. Transmission of SARS-CoV-2: implications for infection prevention. (URL)
6. ASHRAE. Standard 241 – Control of Infectious Aerosols. (URL)
7. Lawrence Berkeley National Laboratory. Filtration performance for airborne particles. (URL)
8. CDC/NIOSH. Germicidal Ultraviolet (GUV) for Air Disinfection. (URL)
9. NIOSH. Upper-Room Ultraviolet Germicidal Irradiation Guidelines. 2009. (URL)
10. Wells WF. Airborne Contagion and Air Hygiene. (URL)
11. Handler MZ et al. Journal of the American Veterinary Medical Association. 2020. PMID: 33064607. (URL)

Annette Uda is the president and founder of Aerapy UV Disinfection Technology. She serves on ASHRAE committees, including TC 2.9 (Ultraviolet Air and Surface Treatment), GPC 37 (Upper-Air UV Disinfection Guidelines), SPC 234 (Method of Testing for Particle and Microorganism Removal or Inactivation), and SSPC 161 (Air Quality within Commercial Aircraft). She has provided UV system design and implementation support for peer-reviewed research published in JAVMA and offers educational training for engineering firms seeking evidence-based approaches to airborne pathogen mitigation. She may be reached at Info@Aerapy.com.