How is Covid-19 (Coronavirus disease 2019) transmitted and what are the ways to prevent its spread?

COVID-19 Transmission and Prevention

COVID-19 is primarily transmitted through respiratory droplets and direct contact with contaminated surfaces, with aerosol transmission occurring during specific high-risk procedures or in enclosed spaces with prolonged exposure. 1

Primary Transmission Routes

Respiratory Droplet Transmission

• SARS-CoV-2 spreads predominantly through respiratory droplets generated by coughing and sneezing, which can travel up to 2 meters and land on mucosal surfaces (nose, mouth, eyes) of nearby individuals. 1
• Droplets are relatively large particles that settle from the air rather than remaining airborne for extended periods. 1
• Even asymptomatic individuals can shed virus and transmit infection through respiratory droplets during normal breathing. 1, 2

Contact Transmission

• The virus remains viable on contaminated surfaces for hours to days depending on the surface type, making fomite transmission a significant route. 1
• Physical contact with SARS-CoV-2-contaminated surfaces followed by touching the face (mouth, nose, eyes) allows viral entry into the body. 1
• Direct contact with infected persons or their secretions facilitates transmission. 1

Aerosol Transmission

• Aerosol transmission occurs with prolonged exposure to high concentrations of viral aerosols in enclosed, poorly ventilated environments. 1
• Aerosol-generating procedures create the highest transmission risk, ranked in descending order: tracheal intubation, tracheostomy, non-invasive ventilation, and mask ventilation. 1
• Other aerosol-generating procedures include bronchoscopy, cardiopulmonary resuscitation, tracheal suctioning without closed systems, and ventilator circuit disconnection. 1, 2

Prevention Strategies

Personal Protective Measures

• Hand hygiene is the most critical prevention measure: wash hands with soap and water for 20-40 seconds or use alcohol-based hand sanitizer regularly. 1
• Avoid touching eyes, nose, or mouth with unwashed hands. 1
• Maintain physical distancing of at least 2 meters from others. 1, 3
• Wear face masks according to local policies, particularly in crowded settings. 1

Environmental Precautions

• The virus can be inactivated by heating at 56°C for 30 minutes, 75% ethanol, chlorine-containing disinfectants, and peroxyacetic acid (note: chlorhexidine is ineffective). 1
• Ultraviolet light effectively inactivates the virus. 1
• Regular disinfection of frequently touched surfaces reduces fomite transmission. 1

Healthcare Worker Protection

• For aerosol-generating procedures, healthcare workers must use N95/FFP2 respirators (blocking 95-99% of aerosol particles), along with gloves, gown, and eye protection. 4, 3
• For routine care without aerosol-generating procedures, surgical/medical masks with eye protection, gown, and gloves are the minimum requirement. 4, 3
• Aerosol-generating procedures should be performed in negative pressure rooms when available. 4, 3
• The most experienced personnel should perform high-risk procedures to minimize duration and number of attempts. 4, 3

Behavioral Modifications

• Avoid crowded places and close contact with infected individuals. 1
• Practice respiratory etiquette: cover coughs and sneezes with tissue or elbow. 1
• Discourage non-essential travel during outbreaks. 1
• Implement social distancing measures in workplaces and public spaces. 1

High-Risk Populations and Settings

Vulnerable Individuals

• Elderly individuals (especially those ≥85 years) and persons with underlying conditions (hypertension, diabetes, cardiovascular disease, chronic respiratory disease, cancer) face significantly higher risk of severe disease and death. 1
• Healthcare workers are at particularly high risk due to close contact with infected patients and exposure to high viral loads. 1
• Workers in occupations with continuing public exposure (first responders, service workers, drivers) face elevated transmission risk. 1

High-Risk Settings

• Healthcare facilities, particularly during aerosol-generating procedures, represent the highest transmission risk environments. 1
• Closed communities and workplaces with inadequate infection control can experience major outbreaks. 1
• Enclosed spaces with poor ventilation and prolonged exposure facilitate aerosol transmission. 1

Critical Caveats

• Asymptomatic carriers can transmit infection, making universal precautions essential during the pandemic. 1, 2
• The incubation period ranges from 1-14 days (most commonly 3-7 days), during which infected individuals may unknowingly spread the virus. 1
• Healthcare workers exposed to high viral loads during procedures may develop more severe illness if infected. 1
• Lungs damaged by smoking, air pollution, or occupational exposures (silica, asbestos, coal dust) face heightened infection risk and worse outcomes. 1