Aerosol refers to a suspension of tiny solid particles or liquid droplets in air or another gas.

In infectious disease transmission, aerosols are fine respiratory particles—typically less than 5 microns in diameter—that are expelled when a person breathes, speaks, coughs, or sneezes.

These particles can remain suspended in air for a long period and travel over distances greater than six feet, particularly in poorly ventilated indoor environments.

Why aerosols matter for infection control

Aerosols are central to understanding how many respiratory pathogens spread.

Misunderstandings in historical frameworks

The traditional distinction between “droplets” and “airborne” transmission created a false binary.

Examples of respiratory aerosol generation

Most respiratory activities generate a continuum of particle sizes, including infectious aerosols.

• Normal breathing
• Speaking softly or loudly
• Coughing
• Sneezing
• Singing
• Shouting

Settings where aerosol transmission is high risk

• Enclosed indoor spaces
• Poorly ventilated buildings
• Health care settings
• Public transportation
• Gatherings with loud vocal activity

These environments facilitate the buildup and spread of infectious aerosols.

Key infectious diseases spread by aerosols

• COVID-19 (SARS-CoV-2)
• Influenza
• Respiratory syncytial virus (RSV)

Emerging concerns and future implications

• Aerosol transmission under investigation for mpox
• Growing evidence of aerosol spread in seasonal outbreaks
• Need for updated surveillance and research methods

Lessons from the COVID-19 pandemic

How aerosol science reshaped policy

Recognition of aerosol transmission reshaped infection prevention and control.

• Superspreading events in indoor settings highlighted aerosol risks
• Shift from surface disinfection to air-based interventions
• Increased emphasis on high-filtration masks

Practical interventions to reduce aerosol spread

Effective aerosol control requires multiple strategies.

• Improving indoor ventilation systems
• Using HEPA filters or portable air cleaners
• Limiting occupancy and exposure time

Protective equipment and behavior

Personal protection plays a critical role in mitigating aerosol risks.

• Wearing N95, FFP2, or KN95 masks
• Avoiding crowded indoor environments
• Prioritizing outdoor activities when possible

Institutional and policy response

Many public health agencies revised their guidance to reflect aerosol risks.

• CDC updated recommendations for indoor air quality
• WHO incorporated aerosol transmission into COVID-19 guidance
• National building standards began to prioritize ventilation

Public awareness and communication

Clear messaging about aerosols helps individuals make safer choices.

• Explaining how aerosols behave indoors
• Using risk-based language (e.g., “inhalation transmission”)
• Educating on how to improve air quality

A new paradigm in infection control

Clean air must be treated as essential public health infrastructure.

What this means for public health systems

• Incorporate aerosol science into disease modeling
• Train health professionals on airborne risks
• Build air quality considerations into public health policies

Investments to prevent future pandemics

• Fund indoor air monitoring systems
• Retrofit public buildings with ventilation upgrades
• Research aerosol dynamics across pathogens

Modernizing infection prevention

Policy and infrastructure recommendations

• Establish indoor air standards for public spaces
• Mandate ventilation assessments in schools and workplaces
• Incentivize adoption of filtration and UV disinfection systems
• Embed aerosol precautions into pandemic preparedness plans
• Develop real-time indoor air risk communication tools