A novel coronavirus emerged in China in 2019 named as SARS-CoV-2, become a pandemic. Scientists, Researchers and Health care professionals are still learning about it. It is an endeavor to compile all the possible modes of transmission of the virus from different reputed sources, so that it can help to understand the behavior of the virus and suitably modify the preventive measures practiced at present. This may change as more knowledge acquired on the virus.
COVID-19 Outbreak Associated with Air Conditioning in Restaurant, Guangzhou, China, 2022:

1. During January 26–February 10, 2020, an outbreak of 2019 novel coronavirus disease in an air-conditioned restaurant in Guangzhou, China, involved 3 family clusters. The airflow direction was consistent with droplet transmission. To prevent the spread of the virus in restaurants, the researchers recommend increasing the distance between tables and improving ventilation. Reference

2. Aerosol and Surface Distribution of Severe Acute Respiratory Syndrome Coronavirus 2 in Hospital Wards, Wuhan, China, 2020

Contamination was greater in intensive care units than general wards. Virus was widely distributed on floors, computer mouse, trash cans, and sickbed handrails and was detected in air ≈4 m from patients.

In this study, researchers tested surface and air samples from an intensive care unit (ICU) and a general COVID-19 ward (GW) at Huoshenshan Hospital in Wuhan, China.

The study led to 3 conclusions. First, SARS-CoV-2 was widely distributed in the air and on object surfaces in both the ICU and GW, implying a potentially high infection risk for medical staff and other close contacts. Second, the environmental contamination was greater in the ICU than in the GW; thus, stricter protective measures should be taken by medical staff working in the ICU. Third, the SARS-CoV-2 aerosol distribution characteristics in the GW indicate that the transmission distance of SARS-CoV-2 might be 4 m.

In addition, their findings suggest that home isolation of persons with suspected COVID-19 might not be a good control strategy. Family members usually do not have personal protective equipment and lack professional training, which easily leads to familial cluster infections. During the outbreak, the government of China strove to the fullest extent possible to isolate all patients with suspected COVID-19 by actions such as constructing mobile cabin hospitals in Wuhan, which ensured that all patients with suspected disease were cared for by professional medical staff and that virus transmission was effectively cut off. As of the end of March, the SARS-COV-2 epidemic in China had been well controlled. Reference

3. Transmission Potential of SARS-CoV-2 in Viral Shedding Observed at the University of Nebraska Medical Center

SARS-CoV-2 is shed during respiration, toileting, and fomite contact, indicating that infection may occur in both direct and indirect contact. Reference

4. The Role of Particle Size in Aerosolised Pathogen Transmission:

In a review, particle sizes generated from breathing, coughing, sneezing and talking showed healthy individuals generate particles between 0.01 and 500 μm, and individuals with infections produce particles between 0.05 and 500 μm. This indicates that expelled particles carrying pathogens do not exclusively disperse by airborne or droplet transmission, but avail of both methods simultaneously and current dichotomous infection control precautions should be updated to include measures to contain both modes of aerosolised transmission. Reference

5. Respiratory Virus RNA is Detectable in Airborne and Droplet Particles

In a study, on breathing, 58% of participants produced large particles (>5 µm) containing viral RNA and 80% produced small particles (≤5 µm) carrying viral RNA. On coughing, 57% of participants produced large particles containing viral RNA and 82% produced small particles containing viral RNA. Forty five percent of participants produced samples positive for hRV viral RNA and 26% of participants produced samples positive for viral RNA from parainfluenza viruses. Reference

6. Potential for Airborne Transmission of Infection in the Waiting Areas of Healthcare Premises: Stochastic Analysis Using a Monte Carlo Model:

The researchers have found that under normal circumstances the risk of acquiring a TB infection during a visit to a hospital waiting area is minimal. Likewise, the risks associated with the transmission of influenza, although an order of magnitude greater than those for TB, are relatively small. By comparison, the risks associated with measles are high. While the installation of air disinfection may be beneficial, when seeking to prevent the transmission of airborne viral infection, it is important to first minimize waiting times and the number of susceptible individuals present, before turning to expensive technological solutions. Reference

7. COVID-19 Can Travel on Shoes:

The floor swabs also had a high rate of positive tests, potentially due to virus droplets falling on the ground. Half of the ICU staff’s shoes also tested positive. As medical staff walk around the ward, the virus can be tracked all over the floor, as indicated by the 100% rate of positivity from the floor in the pharmacy, where there were no patients.

Reference
8. How COVID-19 Spreads

COVID-19 is thought to spread mainly through close contact from person-to-person in respiratory droplets from someone who is infected. People who are infected often have symptoms of illness. Some people without symptoms may be able to spread virus. Spread from contact with contaminated surfaces or objects. This virus is spreading more efficiently than influenza, but not as efficiently as measles, which is highly contagious. Reference

9. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1

Aerosol and fomite transmission of SARS-CoV-2 are plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days (depending on the inoculums shed.

SARS-CoV-2 remained viable in aerosols for 3 hours in experimental conditions, with a reduction in infectious titer from 10^3.5 to 10^2.7 TCID₅₀ per liter of air.

SARS-CoV-2 was more stable on plastic, viable virus was detected up to 72 hours after application to this surface, although the virus titer was greatly reduced (from 10^3.7 to 10^0.6 TCID₅₀ per milliliter of medium after 72 hours.

SARS-CoV-2 was stable on stainless steel, although the virus titer was greatly reduced from 10^3.7 to 10^0.6 TCID₅₀ per milliliter after 48 hours.

On copper, no viable SARS-CoV-2 was measured after 4 hours.

On cardboard, no viable SARS-CoV-2 was measured after 24 hours

Reference Reference

10. Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations; WHO

Respiratory infections can be transmitted through droplets of different sizes: when the droplet particles are > 5-10 μm in diameter they are referred to as respiratory droplets, and when they are < 5μm in diameter, they are referred to as droplet nuclei.According to current evidence, COVID-19 virus is primarily transmitted between people through respiratory droplets and contact routes.In an analysis of 75,465 COVID-19 cases in China, airborne transmission was not reported. Reference
11. Speed of a Sneeze.

The largest droplets rapidly settle within 1 to 2 m away from the person. The smaller and evaporating droplets are trapped in the turbulent puff cloud, remain suspended, and, over the course of seconds to a few minutes, can travel the dimensions of a room and land up to 6 to 8 m away. Reference

12. Coughing and Aerosols

A maximum airspeed of 8 m per second (18 mph) has been observed by researchers, averaged during the half-second cough. The cough plume may project infectious aerosols into the surrounding air.

Reference

13. Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering

It was calculated that the original diameters of the respiratory drop lets ranged from1to 2000 micron that 95% were between 2 and 100 micron and that the most common were between 4 and 8 micron. Reference

14. Seasonality of Respiratory Viral Infections

There can be possible seasonal determinants in the epidemics of respiratory viruses as well as host factors affected by these contributing factors. These include seasonal changes in temperature, absolute humidity (AH), sunlight, vitamin status, and host behavior. Animal transmission studies with guinea pigs and ferrets have revealed that high RH (>60%) and low RH (<40%) seems to allow viability of influenza viruses in droplets, while in intermediate RH (40% to 60%) viruses become inactivated.

Since, the type II alveolar cells, where the angiotensin-converting enzyme II concentrated, are located deep in the respiratory tract, are not reachable by respiratory droplets with a diameter of more than 5 micrometers, it appears likely that at least, the severe cases of COVID-19 with viral pneumonia, are the result of air borne transmission events.

The combination of low humidity, temperature, and sunlight may trigger an impairment of the local and systemic antiviral defense mechanisms, leading to the increased host susceptibility to the respiratory viruses in winter.

In addition to vaccines and antiviral drugs, non-pharmaceutical interventions to prevent respiratory infections are gaining attention. Lifestyle (eating healthy, sleeping more than 7 h/day) and hygiene practices (washing hands, wearing facemasks) are known to increase antimicrobial resistance and prevent transmission, respectively. In addition to these measures, we might consider controlling the indoor environment to combat respiratory infections. Such interventions with humidifiers (RH~45) have been realized since the 1960s with promising results. Reference

15. Possible Preventive Measures¹:

1. The first and foremost message emerging out of the researches is Social Distancing:

(i) 2 meters (6 feet), instead of 1 meter, wherever possible, like market places, malls, hospital waiting areas, restaurants, and offices etc..

(ii) Quick disposal of patients and customers in commercial establishments (Malls & Restaurants)

(iii) At least, 1 meter (3 Feet) distance in Triage facility in Hospital and during home quarantine (If, no separate room is available).

(iv) Barrier (Glass) communication at Reception Counters in Acute Respiratory Infection or Fever Clinic

(v) Restriction of entry of non-essential health care staff to the ICU/Rooms of COVID-19 patients, multi-tasking.

(vi) Sanitization of footwear, like two coir mat system²; standing for 1 minute on a mat soaked with 1% Sodium Hypochlorite solution, then drying foot on 2^nd coir mat.

(vii) As health care persons (as well as some other professions, like saloon staff), who cannot maintain distancing, Correct use of PPEs (separate donning & doffing) as recommended for ICU and other places.

(viii)         Healthcare supervised quarantine, in lieu of home quarantine
2. Use of Facemasks: At least, Home-made mask for all, while going out (only to collect essential items). Standard PPEs for Hospital staff as per protocol.
3. Use of HEPA (High Efficiency particulate Air Filter) filters in Hospital settings (Acute Respiratory Infection treatment ICU/WARDS).
4. Following Good Hand Hygiene practice (Minimum 30 second, instead of 20 seconds) & Cough Etiquette.
5. Correct way of hand Sanitization (20 seconds, six steps as hand washing)
6. Maintaining healthy Lifestyle (eating healthy, sleeping more than 7 h/day), physical exercise (at least in Indoor), taking fresh fruits, and Vitamin D (Exposure to Sun is better).
7. Humidifier in Rooms to maintain RH (Relative Humidity = ~45).
8. Providing correct PPEs to patient.
9. Box-Shield Protected (as shown in NEJM video) Endotracheal Intubation/Ex-tubation/Splash generation procure.
10 Sanitization of frequently touched places, Bed-rail of patient, Door-knobs, Computer Key-board & Mouse, Lifts, stair-case rail, Hospital trolleys/stretchers/wheel-chairs, and handles of trolley/cart in Malls etc.. Sanitization of card boards (files, not required, if, not exposed; however, UV sterilizer can be used or exposed to Sun).
11. Cupper coating of steel surfaces in Hospital Settings (Like, bed-rails, bathroom door-knobs, and wheel-chairs etc.).
12. Covering the wheel-chair and stretchers with rubber mackintosh sheets that can be sanitized later.
13. Designing AIR-Conditioners with HEPA filters for hospital use, like used in Airplanes.
14. Managing laundry according to SoP (Soaking in detergent & hot water-washing/Use Hypochlorite) with correct use of PPEs.
15. Vaccination (When available).

(A Paradip Port Trust Hospital document)

Credit:

WHO

CDC

NEJM

Worldmeter Reference

WebMD

Acknowledgements

1. Sri Rinkesh Roy, IRTS, Chairman, Paradip Port Trust for reviewing of the article

2. Dr Raja Ravi Varma, Chief Medical Officer, Chennai Port Trust for use of hypochloride soaked mat