Different Modes of Transmission and Containment Strategies for COVID-19

Coronavirus disease (COVID-19) is a respiratory infectious ailment caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The first outbreak of this disease occurred in China and declared a pandemic in a very short period of time. SARS-CoV-2 gets transmitted mainly through the respiratory tract by droplets or respiratory secretions, and by direct contact with the infected person as well as indirect contact through touching the contaminated surface accompanied by poor hygiene practice. Until the vaccine, therapeutic agent or any other treatment modality gets approved; contact tracing and management , social distancing, personal hygiene, respiratory etiquette, and environmental decontamination are the prime factors to be considered for transmission containment and hence for appropriate safety measures for COVID-19 which is possible with the support of social work from community level.


BACKGROUND
The COVID-19 is an infectious respiratory disease caused by a new coronavirus strain named as SARS-CoV-2, which first emerged in Wuhan, China, and reported to the world health organization (WHO) on 31 December 2019 as pneumonia of unknown source, later termed as COVID-19. 1,2The symptoms occur within two weeks after exposure that may range from mild type of fever, cough, headache, fatigue to shortness of breath, acute respiratory distress syndrome (ARDS), pneumonia, and shock. 3Thailand reported the first official case outside the epicentre on 13 January 2020.On 30 January 2020, the

Viewpoints
Author Info: 1 Shree Birendra Hospital; Nepalese Army Institute of Health Sciences, Kathmandu-44600, Nepal 2 Punjab University College of Pharmacy, University of the Punjab, Lahore-54000, Pakistan Corresponding Author: Sitaram Khadka sitaramkhadka5693@gmail.com 00977-9851077589 ORCiD outbreak was announced as a public health emergency of international concern (PHEIC) and later declared a pandemic on 11 March 2020 by the WHO. 1 Around the globe, as of 09 May 2020, the total confirmed cases of COVID-19 stand at 3,767,744, including 259,593 deaths, where the United States of America has reported the maximum confirmed cases, i-e., 1,215,571 with a death toll of 67,146. 4ttps://doi.org/10.46405/ejms.v2i2.50

MECHANISMS AND MODES OF TRANSMISSION OF COVID-19
SARS-CoV-2 belongs to the genera β-coronaviruses, an enveloped non-segmented positive-sense RNA virus, with genome sequence almost 96.2% similar to a bat coronavirus RaTG13 -implying bat as reservoir to SARS-CoV-2 virus. 5Thus, it is reasonable to deduce that SARS-CoV-2 might have transmitted from bat through an unspecified intermediary host to humans.The virus gains entry by binding to a host cell receptor followed by fusion with the cell membrane and lung epithelial cells as primary targets.The human-to-human transmission occurs by holding between the receptor-binding domain of virus spikes and the cellular receptor recognized as angiotensin-converting enzyme 2 (ACE2) receptor. 6The incubation period of SARS-CoV-2 is approximately 3 to 7 days and COVID-19 is contagious in the course of latency period.It is extremely transmissible in humans, especially in the geriatrics and people with co-morbid conditions. 7man-to-human transmission of SARS-CoV-2 takes place mainly through the respiratory route by droplets or respiratory secretions. 8Studies have also shown that even moderate viral protein concentrations in droplets gives virus the ability to expand exponentially -suggesting its high transmission capacity. 9The chances of droplet transmission increase with close contact, i-e., within 1 meter distance with COVID-19 positive people, which increases the propensity of viral entry via the mucosal membranes of the mouth, nose and eyes after exposure to potentially infective respiratory droplets.
Attempts have been made to isolate COVID-19 RNA in samples of air from places where COVID-19 patients were quarantined10, but the results are controversial, as some claim its presence and some otherwise.It is further argued that the detection of COVID-RNA in the environment using PCR test does not warrant the presence of a viable and transmissible virus, therefore, further detailed studies are required to confirm these claims. 10hough in some studies airborne transmission was not reported. 11succeeding dissemination by sneezing or coughing, droplets containing the coronavirus have been airborne, and it has been reported that the virus stands vital in that position until 3 hours when artificially nebulized as aerosol. 1

Characteristics
Safety measures Touching fomites in the environment around the infected person.can transmit the virus through the mouth, nose or eye if touched with unclean hand Wearing gloves, frequent hand washing through soap or using sanitizer, decontamination of suspected objects Feco-oral route 12 Virus has been detected in fecal swab Limiting movement, wearing gloves, frequent hand washing through soap or using sanitizer, decontamination of suspected objects Mother to fetus 6 No evidence is seen in caesarean birth Personal hygiene maintenance transmission, directly by contacting the infected person or indirectly by touching the contaminated surfaces in the immediate environment.SARS-CoV-2 has also been isolated from patient's faecal swabs, indicating the possibility of transmission via multiple routes. 12There is no clinical evidence of COVID-19 transmission from mother to foetus in caesarean cases nor any such proof for vaginal birth6.Though, no scientific evidence exists that the survival of SARS-CoV-2 outside the body is comparable to Middle East respiratory syndrome (MERS), yet the claim is highly premature currently.Nonetheless, there are evidences that COVID-19 can spread via fomite contacts, e.g., washroom, escalators switch, taps, door knobs, utensils, etc. 13 According to published reports, coronavirus can live for hours outside the host, such as aluminium, sterile sponges or latex surgical gloves, surging the opportunity for transmission via touch. 14The study suggested that the samples taken from toilet utensils, such as toilet bowl and sink were found positive, signifying it as a potential source of transmission, though the samples became negative post cleaning. 11 the same study, the authors claimed that the tested air samples were found negative, however, there could be a number of implicit limitations related to these findings, i-e., no viral culture to demonstrate viability, inconsistent methodology, small sample size, and small fraction to total air volume where the air exchange may have diluted the contamination. 11The WHO and the centre for disease control and prevention (CDC) advises health care workers and other staff to maintain 3-6 feet distance from the patient to prevent the transmission of the disease.Peak exhalation speeds may extend up to 33 to 100 feet per second, generating a cloud that can span around 23 to 27 feet. 15Table 1 shows the different modes of transmission and safety measures of COVID-19.

TRANSMISSION CONTAINMENT STRATEGIES
As contaminated fomites play a substantial role in the transmission of SARS-CoV-2, decontamination by repeated cleaning of the surface is a mandatory requirement to halt the transmission of virus to mitigate COVID-19 transmission.The better understanding of physiology of the host, pathogenesis, and epidemiological escalation of the disease are keys to achieve substantial improvements in disease remission and to prevent disease transmission to the vulnerable population 15 .
The risk of nosocomial infection can be managed by inpatient control measures in hospitals by plan, do check, and act (PDCA) cycle 16 .The use of N95 or other surgical masks can help to control the spread of disease, which relies on the capacity of the mask to hold or restrict the high-momentum gas cloud emission.Protective and source control masks, and personal protective equipment (PPE) with the property to hold and protect the potential host from high-momentum multiphase turbulent gas clouds ejected during sneezing or coughing are essential protective gears to contain its spread 15 .
The contact tracing method of immediate scale up action by communities with trained individuals for identification of people with travel history from a high risk area and people in contact with the suspected or infected individual, and their quarantine, test or isolation and treatment, if needed, in the nearby healthcare facility for transmission containment act as a key strategy to break the chain of spread of COVID-19 17 .The public health awareness program for preventive measures can be applied at the community as well as the central level for the transmission containment, and safety measures.
Herd immunity can be one of the strategies of safety measure that helps in transmission containment of disease, but as SARC-CoV-2 has property of mutation, antibodies from a previous infection provide protection for only a short period of time, and its high risk of severity including death suggests to maintain social distancing from the time of high infection rate for maintenance of level of infection until vaccine develops 18 .
Though not any therapeutic or prophylactic agents as well as treatment modalities have been approved, several antivirals and other drugs are being practiced to treat COVID-19, mostly focussing on the symptomatic treatment based on patient's status 3 .Drugs like hydroxychloroquine/ Azithromycin combination, ivermectin, oseltamivir, ganciclovir, Interferons, lopinavir/ritonavir combinations 19 and some other antibiotics are being practiced, taking care of their adverse events, along with the supportive care according to the WHO interim guidance for COVID management 3 .Remdesivir has recently been authorized by FDA for emergency use against COVID-19 20 .Different treatment modalities like convalescent plasma therapy have also been practiced with better safety profile.Several clinical trials are now underway to discover more specific and efficacious drugs, vaccines, and treatment modalities as well.
Thus, for those taking care of COVID-19 patients and are vulnerable to contagion, droplet and contact; must adopt safety measures, such as social distancing, limiting movement, wearing mask/ gloves/goggles, frequent hand washing with soap or using sanitizer, and frequent decontamination practices along with apt measures to prevent airborne miasma in a clinical setting by adopting pre-emptive risk assessment and safety precautions to curtail disease transmission. 10,21

CONCLUSION
The continuous global spread even after the passing of four months suggests the highly contagious nature of COVID-19 due to therapeutic qualm regarding the unavailability of an approved agent for treatment.Similarly, there is considerable ambiguity in the exact in depth understanding of the mode of its transmission and specific safety measures to prevent its spread.The consequential environmental contamination by patients with SARS-CoV-2 through respiratory droplets and faecal shedding suggests that the environment is one of the potential modes of transmission, therefore, there is a need for careful constancy to environmental hygiene practices.The utmost consideration must be given to personal hygiene such as frequent hand washing, respiratory etiquette, environmental decontamination, and social distancing for the containment of the disease.This is possible with the consistency of workforce from the community at the local to the central level within one umbrella, and of course social work from people has a pivotal role to accomplish such task.