Airborne and Surface Transmission of SARS-CoV-2 in Hospital Settings: Evidence from a COVID-19 Dedicated Hospital in India

1. Introduction

The COVID-19 pandemic, driven by the SARS-CoV-2 virus, has placed immense strain on healthcare systems globally [1]. A key factor in controlling the spread of the virus is understanding its transmission methods. While SARS-CoV-2 primarily spreads through respiratory droplets, emerging evidence emphasizes the role of airborne transmission [1, 2]. Smaller aerosol particles can linger in the air for extended periods, potentially infecting those who inhale them [3]. Additionally, fomite transmission, where the virus remains viable on surfaces and can infect individuals upon contact, has also been documented. These transmission routes pose significant risks, particularly in hospital settings where COVID-19 patients are concentrated, and healthcare workers are on the front lines [4, 5].

Hospital environments are particularly vulnerable to both airborne and surface transmissions due to the high density of individuals, including severely ill patients who shed large amounts of the virus. This increases the risk of contamination, especially in poorly ventilated areas and on frequently touched surfaces such as door handles, bed rails, and medical equipment. Understanding the dynamics of airborne and surface transmission in these settings is critical for implementing effective infection control measures and safeguarding healthcare workers, patients, and visitors [6, 7, 8].

This chapter provides evidence-based insights into the transmission of SARS-CoV-2 through the air and on surfaces within a COVID-19 dedicated hospital in India [9]. The study aims to evaluate the presence of the virus in various areas of the hospital, identify contamination patterns based on patient load and proximity to infected individuals, and discuss the implications of these findings for infection prevention and control strategies [7]. Through these insights, the chapter seeks to enhance the understanding of viral transmission pathways and inform policies to reduce the risk of infection in healthcare environments [10].

2. Background

Global research has extensively studied SARS-CoV-2 transmission since the pandemic began, focusing on both airborne and surface routes. Initially thought to spread mainly through respiratory droplets, studies have shown that smaller aerosols, which remain suspended in the air for long periods, also play a significant role, particularly in enclosed, poorly ventilated spaces like hospitals [11]. Additionally, the virus has been found on high-touch surfaces such as door handles and medical equipment, raising concerns about fomite transmission [12, 13, 14].

Hospitals are key environments for studying viral transmission, given their high density of infected patients and healthcare workers. These settings face unique challenges, such as overcrowding, inadequate ventilation, and high patient turnover, all of which increase the risk of airborne and surface transmission [15, 16]. Healthcare workers, often in close contact with COVID-19 patients, are at heightened risk, despite personal protective equipment (PPE) measures [17, 18]. Frequent disinfection is crucial but difficult to maintain in busy areas, making hospitals particularly vulnerable to viral spread [1, 19, 20].

Understanding these transmission dynamics is essential for guiding infection prevention and control (IPC) strategies, especially in resource-limited hospitals. By addressing these challenges, hospitals can better protect healthcare workers and patients, minimizing the risk of SARS-CoV-2 transmission [5].

3. Hospital setting and study design

The study was conducted at Lok Nayak Hospital (LNH) in Delhi, India, a major public hospital designated for COVID-19 treatment. LNH handled both moderate and severe cases, offering services such as intensive care, emergency treatment, and general medicine. Located in one of the world’s most densely populated cities, the hospital experienced high patient turnover, making it ideal for studying airborne and surface transmission of SARS-CoV-2 [9, 21].

The hospital’s wards, including the ICU, medicine, and emergency wards, were adapted to accommodate COVID-19 patients. The ICU had advanced ventilation with HEPA filters, while the medicine and emergency wards relied on natural ventilation and air conditioning. This variation allowed for a detailed study of transmission dynamics across different ventilation conditions.

The study, conducted between July 1 and September 25, 2020, focused on sampling air and surfaces in the hospital. Air samples were collected from the medicine ward, ICU, and emergency ward, while surface swabs were taken from patient beds, floors, and nursing stations [22, 23, 24]. Air samples were collected at 1- and 3-m distances from patients using a total suspended particulate (TSP) air sampler, while surface samples were collected from frequently touched areas. All samples were tested using RT-PCR to detect SARS-CoV-2 [25, 26, 27].

This design enabled a comprehensive investigation into the spread of the virus, providing insights into both airborne and surface transmission risks in a hospital setting.

4. Sampling methods and procedures

Air sampling was conducted using a total suspended particulate (TSP) air sampler, calibrated to national standards. Equipped with PVDF filters (100 nm), the sampler operated at flow rates of 1.5, 16.7, and 27 LPM for 1-hour periods. It was placed at 1- and 3-m distances from patients in the medicine ward and ICU, while in the emergency ward, it was positioned centrally due to transient patient presence. After each sample, the filter was placed in viral transport media (VTM) and transported to the lab for RT-PCR testing. Negative control samples were taken from a green zone to rule out contamination.

Surface sampling targeted high-touch areas in patient beds, ward floors, and nursing stations. Swabs were collected from 2 square feet areas near patient beds and from tables in nursing stations. These samples were also stored in VTM and sent for RT-PCR analysis.

Sampling locations were chosen based on areas with high viral shedding potential, such as near patient beds in the medicine ward (moderate cases) and ICU (severe cases). In the emergency ward, air sampling captured overall contamination due to high patient turnover. Nursing stations were included to assess healthcare worker exposure [17, 20, 21].

Data collection occurred from July 1 to September 25, 2020, during peak COVID-19 activity. Sampling in the medicine ward and ICU focused on patients admitted within the last 48 hours, while in the emergency ward, air samples were taken during high turnover periods. This method allowed for comprehensive analysis of airborne and surface contamination in the hospital [28].

5. Laboratory analysis

Laboratory analysis for detecting SARS-CoV-2 in air and surface samples primarily used reverse-transcriptase polymerase chain reaction (RT-PCR). This method targeted two genes: the E-gene (for general coronavirus detection) and the RdRp gene (specific to SARS-CoV-2). Air samples, collected using PVDF filters, were processed by extracting RNA, followed by RT-PCR using the STANDARD M nCoV Real-Time Detection kit. Surface swabs were similarly processed, and a cycle threshold (Ct) value below 35 indicated a positive result for SARS-CoV-2.

Although viral culture was not performed due to resource limitations, RT-PCR provided sensitive detection of viral RNA. Quality control measures included using negative controls from COVID-free areas, ensuring accurate sample handling and transport, and employing automated RNA extraction systems to minimize error. The RT-PCR kit used was clinically validated, ensuring reliable detection.

Samples were collected on multiple days from different wards to ensure consistency and reproducibility. These measures confirmed the presence of SARS-CoV-2 in both air and surface samples, ensuring the study’s accuracy and reliability.

6. Results

Air sampling across the hospital wards confirmed the presence of SARS-CoV-2 RNA in the air, particularly near COVID-19 patients. In the medicine ward, the virus was detected at both 1- and 3-m distances, with a higher viral load (lower Ct values) at 1 m, indicating greater contamination closer to the patients. Similar patterns were observed in the ICU, where SARS-CoV-2 was found near ventilated patients. Despite the ICU’s aerosol-generating procedures, viral concentrations were comparable to those in the medicine ward, likely due to similar contamination levels across both settings. In the emergency ward, even brief patient occupancy resulted in viral RNA detection in the air, with viral loads comparable to those measured at 3-m distances in other wards. Figure 1 illustrates the decrease in viral load as distance from the patient increases, highlighting the risk of close-contact airborne transmission.

Surface contamination was widespread in high-contact areas, with SARS-CoV-2 RNA detected on patient beds and floors in both the medicine ward and ICU, confirming these surfaces as potential sources of fomite transmission. Interestingly, nursing stations in these wards, which were separated by physical barriers, showed no contamination. In contrast, the emergency ward, lacking such barriers, exhibited positive surface samples, suggesting higher contamination risks in open-plan areas. Figure 2 shows higher contamination rates on patient beds and floors across all wards, with notable contamination at the nursing stations in the emergency ward.

These findings emphasize a clear correlation between viral load and proximity to infected patients, with samples taken within 1 m showing consistently higher viral loads. Although the ICU had aerosol-generating procedures, its viral concentration remained similar to the medicine ward, likely due to lower patient density. The emergency ward displayed contamination levels comparable to other wards, despite the transient nature of patient stays.

Overall, the results underscore the influence of patient proximity, ward layout, and ventilation on viral transmission, highlighting the need for robust infection control measures to mitigate airborne and surface transmission in healthcare settings.

7. Discussion

The present study provides crucial insights into the airborne and surface transmission of SARS-CoV-2 in a dedicated COVID-19 hospital during the peak of the pandemic. By systematically assessing viral contamination in the air and on high-contact surfaces, our findings contribute to the growing body of evidence regarding the transmission dynamics of SARS-CoV-2 in healthcare settings. The detection of viral RNA in air samples up to 3 m from patients, coupled with extensive surface contamination, underscores the significant role of both aerosolized and fomite-based transmission routes in the nosocomial spread of COVID-19.

One of the key findings of our study is the higher concentration of viral RNA in air samples collected at a 1-m distance compared to those collected at 3 m. This observation aligns with previous studies that have demonstrated the presence of SARS-CoV-2 in aerosols near infected individuals, suggesting that viral load diminishes with increased distance from the source. However, the detection of viral RNA even at a 3-m distance reinforces the potential for airborne transmission beyond the traditionally recognized close-contact range of 1–2 m. This has important implications for infection control practices, emphasizing the need for adequate ventilation and air filtration systems in hospital settings to mitigate the spread of the virus [25].

Surface contamination was widespread across different areas of the hospital, with the highest viral loads detected on patient beds and floors. These findings are consistent with previous studies that have reported significant environmental contamination in healthcare settings, particularly in areas where COVID-19 patients are treated [29, 30]. The high viral presence on patient beds is expected, given their direct and prolonged contact with infected individuals. Contamination of floors, on the other hand, suggests possible viral deposition from respiratory droplets and aerosols, which subsequently settle on surfaces. Healthcare workers and hospital staff may inadvertently contribute to further transmission by coming into contact with these contaminated surfaces and unknowingly transferring viral particles to other locations within the hospital.

The presence of SARS-CoV-2 RNA on nursing stations and other high-touch surfaces such as door handles and medical equipment highlights the potential role of fomites in viral spread [26, 27]. Despite rigorous cleaning and disinfection protocols in place, our study suggests that there may be gaps in current sanitation practices or that rapid recontamination occurs due to frequent human interaction with these surfaces. This calls for enhanced cleaning protocols with increased frequency, as well as the use of more effective disinfectants to ensure complete viral inactivation. Additionally, the findings underscore the importance of consistent hand hygiene among healthcare workers and patients to minimize the risk of fomite-mediated transmission [11, 13, 31].

An important consideration in the interpretation of our results is the distinction between the detection of viral RNA and the presence of infectious, replication-competent virus. RT-PCR, while highly sensitive, identifies genetic material and does not necessarily indicate the presence of viable virus capable of causing infection. Nonetheless, the detection of viral RNA on surfaces and in air samples suggests that the potential for transmission exists and should not be underestimated. Further studies using viral culture techniques would be necessary to confirm the infectivity of detected viral particles and better understand the risk posed by environmental contamination [32, 33, 34].

Our study also highlights differences in viral contamination between different hospital areas, with the highest levels observed in the ICU, followed by the emergency ward and medicine ward. This gradient likely reflects differences in patient acuity, disease severity, and the nature of medical interventions performed in each setting. ICU patients, particularly those receiving high-flow oxygen therapy or undergoing procedures such as intubation, generate higher levels of aerosols, which may contribute to increased airborne viral loads. In contrast, the medicine ward and emergency ward, while still exhibiting significant contamination, may have lower viral concentrations due to variations in patient care activities and ventilation conditions.

The findings of this study reinforce the need for comprehensive infection prevention and control measures tailored to the specific risks associated with airborne and surface transmission. Enhanced ventilation strategies, including the use of HEPA filtration systems and ultraviolet germicidal irradiation (UVGI), should be considered to reduce airborne viral loads in high-risk hospital areas. Additionally, the widespread use of personal protective equipment (PPE), including N95 respirators, face shields, and gloves, remains essential for healthcare workers to minimize the risk of exposure.

Our results also support the continued importance of physical distancing measures within hospital settings. While the detection of viral RNA at a 3-m distance suggests potential for transmission beyond conventional close-contact distances, the highest viral concentrations were still observed closer to patients. This indicates that while maintaining a safe distance remains a critical preventive measure, it should be complemented by other interventions such as mask-wearing and environmental controls to effectively reduce transmission risk.

Limitations of the study should be acknowledged. First, as mentioned earlier, RT-PCR detects viral RNA but does not confirm the presence of infectious virus. Second, variations in environmental factors such as airflow, temperature, and humidity were not systematically assessed in this study, though they are known to influence viral stability and transmission. Future research incorporating viral culture methods and detailed environmental analyses would provide a more comprehensive understanding of transmission dynamics in healthcare settings.

Despite these limitations, our findings have important public health and clinical implications. They reinforce the necessity for stringent infection control measures, not only within hospital environments but also in community settings where similar transmission mechanisms may be at play. The study also highlights the need for continuous monitoring of environmental contamination in healthcare facilities, particularly during outbreaks, to inform evidence-based mitigation strategies [15, 35].

This study provides valuable evidence supporting both airborne and fomite-based transmission of SARS-CoV-2 in a hospital setting. The detection of viral RNA in air samples at distances up to 3 m, coupled with significant surface contamination, highlights the critical need for robust infection control strategies, including enhanced ventilation, rigorous disinfection practices, and adherence to PPE protocols. As the global healthcare community continues to combat COVID-19 and prepare for future pandemics, understanding the environmental persistence and transmission dynamics of SARS-CoV-2 remains essential for optimizing disease prevention and control efforts.

8. Infection control implications

The study underscores the importance of implementing comprehensive infection control measures in healthcare settings treating COVID-19 patients. Improving air ventilation in hospital wards, particularly in high-risk areas like ICUs, emergency rooms, and medicine wards, is essential. Mechanical systems with HEPA filters are recommended, as natural ventilation alone may not provide sufficient air circulation in densely populated hospital spaces. Regular air monitoring should be adopted, allowing hospitals to detect viral contamination in real time and take immediate action if needed [36, 37].

Physical barriers, such as glass partitions between healthcare workers’ stations and patient areas, have proven effective in reducing surface contamination and transmission risks. Healthcare facilities should install such barriers in high-risk zones. Additionally, high-touch surfaces, especially in wards where COVID-19 patients are treated, must be disinfected frequently. Strict cleaning protocols, using effective cleaning agents against SARS-CoV-2, are crucial for maintaining hygiene and minimizing the risk of surface transmission [29, 30, 38].

The importance of air filtration systems, personal protective equipment (PPE), and cleaning protocols is evident in this study. Advanced air filtration, including HEPA filters and ultraviolet germicidal irradiation (UVGI), can help reduce airborne viral particles, particularly in areas where aerosol-generating procedures occur. PPE, including N95 respirators, face shields, gowns, and gloves, remains vital for healthcare workers, especially in areas with high airborne or surface contamination. Ensuring that healthcare workers consistently use appropriate PPE is critical in preventing both airborne and surface transmission [39, 40].

Cleaning protocols play a key role in preventing fomite transmission. High-touch surfaces must be disinfected regularly, with a focus on areas where COVID-19 patients are treated. Healthcare workers should be trained on proper cleaning techniques, and hospitals should enforce stringent cleaning schedules to reduce the risk of transmission [41, 42].

The findings also have broader policy implications for managing infectious outbreaks in hospital settings. Hospitals should adhere to enhanced ventilation standards, ensuring that all wards, especially those treating infectious patients, are equipped with adequate air filtration systems. Additionally, policies enforcing the mandatory use of PPE should be strictly followed, and healthcare facilities must maintain sufficient PPE supplies to avoid shortages during outbreaks [15, 35, 43].

Infection control policies should incorporate airborne transmission precautions, mandating the use of N95 respirators in high-risk areas. Regular surface disinfection protocols must be enforced, especially in high-traffic areas such as emergency wards. Hospitals should also implement real-time surveillance systems for air and surface monitoring to detect contamination early and adjust control measures as needed [44, 45, 46].

The safety of healthcare workers is paramount, and continuous training in infection prevention, proper PPE use, and hygiene practices is crucial. Hospitals should ensure regular health monitoring and provide psychological support to healthcare workers during outbreaks [47, 48].

The study highlights the importance of a multilayered approach to infection prevention and control in healthcare settings. By improving ventilation, ensuring consistent PPE use, and maintaining strict cleaning protocols, hospitals can reduce the risks of both airborne and surface transmission of SARS-CoV-2 [49, 50]. These findings provide valuable insights for hospital-level practices and broader health policy aimed at protecting healthcare workers and patients during future infectious outbreaks.

9. Limitations of the study

The study had several limitations. A key limitation was the use of RT-PCR, which detects viral RNA but cannot distinguish between live, infectious virus and noninfectious fragments. Without viral culture methods, it is unclear whether the detected RNA was capable of causing new infections. Additionally, the relatively small sample size and the focus on specific hospital areas (medicine ward, ICU, and emergency ward) limit the ability to generalize the findings to the entire hospital or other settings. Variability in patient viral load and contamination over time was not accounted for, and the study was conducted over a short period, coinciding with the pandemic’s peak in Delhi, which may have affected contamination levels [47, 48].

The study also did not examine how contamination might vary during different times of day, such as during shifts or patient turnover, suggesting that longer-term studies are needed to capture these variations.

Future research should address these gaps by including viral culture techniques to assess the infectiousness of detected viral particles and by expanding sampling to a broader range of hospital environments. Longitudinal studies are needed to explore contamination patterns over time, and research on the effectiveness of different ventilation systems and cleaning protocols could provide deeper insights. Additionally, studies on the viability of the virus on different surfaces and intervention strategies, such as air purifiers and UV germicidal irradiation, are recommended to better manage airborne and surface transmission in healthcare settings.

10. Conclusion

This study provided key evidence of SARS-CoV-2 presence in both the air and on surfaces within a COVID-19 hospital in Delhi, highlighting the significance of airborne transmission, especially up to 3 m from patients. Surface contamination near patient beds and floors suggests that fomite transmission is also a risk. These findings stress the need for comprehensive infection control strategies, including improved ventilation, the use of N95 respirators, and regular disinfection of high-contact surfaces.

The broader implications for hospital infection control practices include enhanced airborne precautions, especially in high-risk areas like the ICU, where HEPA filters and robust ventilation systems are necessary. Strict hygiene practices and frequent surface cleaning must be enforced to mitigate transmission risks.

Further research should focus on determining whether detected viral RNA represents live, infectious virus, and expand sampling across various healthcare settings. Future studies should also investigate the effectiveness of different ventilation systems and infection control interventions, helping to refine measures to prevent the spread of SARS-CoV-2 and other pathogens in hospitals.