The virus causing covid 19 is being predominantly considered till date spreading from person to persons by droplet infections and by generating aerosol during intubations or interventions in closed hospital wards, by fomites, by fecal oral routes or through mother to child transmission. It causes asymptomatic to mild to moderate to severe diseases, cytokine storms, coagulopathy, endothelial dysfunctions, pulmonary embolism , acute myocardial infarction, renal failure. It eventually causes death to people of 07% world wide. Mostly people of aged above 50 years died with or without co morbidities like diabetes, hypertension, asthma, COPD etc.
So far both CDC and WHO told that transmission of SARS-CoV-2 can occur through direct, indirect or close contact with infected people through infected secretions such as saliva and respiratory secretions or their respiratory droplets, which are expelled when an infected person coughs, sneezes, talks or sings.
(1) Respiratory droplets are >5-10 μm in diameter whereas droplets <5μm in diameter are referred to as droplet nuclei or aerosols.
(2 ) Respiratory droplet transmission can occur when a person is in close contact (within 1 metre) with an infected person who has respiratory symptoms (e.g. coughing or sneezing) or who is talking loudly or singing.
In these circumstances, respiratory droplets that include viruses can reach the mouth, nose or eyes of a susceptible person and can result in infection.
Indirect contact transmission involving contact of a susceptible host with a contaminated object or surface (fomite transmission) may also be possible as a method of transmissions for SARS cov- 2 Virus.
Airborne transmission is defined as the spread of an infectious agent caused by the dissemination of droplet nuclei (aerosols) that remain infectious when suspended in air over long distances and time.
(3) Airborne transmission of SARS-CoV-2 can occur during medical procedures that generate aerosols.
WHO so far stated that SARS Covid 19 spreads by droplet infections only.
Lack of recognition about the seriousness of the air borne COVID-19 spread by some of the world leaders maysomeo be a reason for the uncontrollable spread of COVID-19. But there may be possible mechanisms that SIRs -COVID 2 may transmit through aerosol (as per this author:
1) a number of respiratory droplets generated as microscopic aerosols (<5 µm) by evaporating,
2) normal breathing and talking results in exhaled aerosols.
Thus, a susceptible person can inhale aerosols, and may become infected if the aerosols contain the virus in sufficient quantity to cause infection within the recipient.
However, the proportion of exhaled droplet nuclei or of respiratory droplets that evaporate to generate aerosols, and of the infectious dose of viable SARS-CoV-2 required to cause infection in another person are not known yet for SARS cov-2 virus.
Some studies found SARS-CoV-2 virus RNA in air samples within aerosols for up to 3 hours in one study (5 ) and 16 hours in another, which also found viable replication-competent virus (6).
These findings were from experimentally induced aerosols that do not reflect normal human cough conditions.
Some Studies conducted in health care settings where symptomatic covid 19 patients were cared for but where aerosol generation procedure were not performed reported the presences of SARS Covid 2 RNA in air spaces (5,6) but quantity of RNA detected were however low (7,8).
If the fact is that aerosols are not generated at all by the infected persons how then some outbreak reports related to SARI wards, Covid wards, within hospitals, within OPDs, within fever clinics, doctors and health care workers are infected in-spite of full PPE, N95 masks, careful donning and doffing, hand wash with 70% alcohol and succumbed to death.
According to this author aerosol generation is also possible in indoors, in out door spaces, in crowded spaces, in restaurants or in gyms or in fitness classes. It may be combined with droplet transmission.
In these events, short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out.
To prevent air borne transmission en mass use of N95 masks, face covering are necessary. Masks and face coverings prevent both airborne transmission by blocking atomization and inhalation of virus-bearing aerosols and also contact transmission by blocking viral shedding of droplets.
On the other hand, physical distancing, quarantine, and isolation, in conjunction with hand sanitizing, can minimize contact (direct and indirect) transmission but do not protect at all against airborne transmission.
Ventilation is the process providing outdoor air spaces to remove quickly the room air and replacements of air for periods of time.
So replace contaminated air with clean air. Keep open the doors of shops, offices, schools, kinder-gardens, library, restaurant, public transports. Avoid air re circulation through air conditioning machine. Use germicidal like Hypocholorite or hydrogen peroxide solution in atmospheric air in all hospital environment. Sanitise through large guns by municipal corporations the atmospheric air and buildings of hospitals and nursing homes where covid patients and SARI patients are treated, which are considered red or orange containment zones,
Reference:
1] Luo L, Liu D, Liao X, Wu X, Jing Q, Zheng J, et al. Modes of contact and risk of transmission in COVID-19 among close contacts (pre-print). MedRxiv. 2020 doi:10.1101/2020.03.24.20042606
2] Infection Prevention and Control of Epidemic-and Pandemic-prone Acute Respiratory Infections in Health Care. Geneva: World Health Organization; 2014
3] Advice on the use of masks in the
context of COVID-19. Interim guidance. Geneva: World Health Organization; 2020
4] Gralton J Tovey TR, McLaws M-L, Rawlinson WD. Respiratory Virus RNA is detectable in airborne and droplet particles. J Med Virol. 2013;85:2151-9.
5] . Van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N Engl J Med. 2020;382:1564-7
6] Fears AC, Klimstra WB, Duprex P, Weaver SC, Plante JA, Aguilar PV, et al. Persistence of Severe Acute Respiratory Syndrome Coronavirus 2 in Aerosol Suspensions. Emerg Infect Dis 2020;26(9).
7] Ma J, Qi X, Chen H, Li X, Zhan Z, Wang H, et al. Exhaled breath is a significant source of SARS-CoV-2 emission (pre-print). MedRxiv. 2020 doi: 10.1101/2020.05.31.2011515
8] Ma J, Qi X, Chen H, Li X, Zhan Z, Wang H, et al. Exhaled breath is a significant source of SARS-CoV-2 emission (pre-print). MedRxiv. 2020 doi:10. 1101/2020.05.31.20115154
Abridged from a letter to the editor, British Medical Journal, published on July 16, 2020.
