key: cord-0780574-6xvbk2f1 authors: Chan, E. Y. Y.; Shahzada, T. S.; Sham, T. S. T.; Dubois, C.; Huang, Z.; Liu, S.; Ho, J. Y.-e.; Hung, K. K.; Kwok, K. O.; Kayano, R.; Shaw, R. title: Non-pharmaceutical behavioural measures for droplet-borne biological hazards prevention: Health-EDRM for COVID-19 (SARS-CoV-2) pandemic date: 2020-05-29 journal: nan DOI: 10.1101/2020.05.29.20116475 sha: f038903ca3745630561e7097f55c5b46a3f5905b doc_id: 780574 cord_uid: 6xvbk2f1 Introduction: Non-pharmaceutical interventions to facilitate response to the COVID-19 pandemic, a disease caused by novel coronavirus SARS-CoV-2, are urgently needed. Using the WHO health emergency and disaster risk management (health-EDRM) framework, behavioural measures for droplet-borne communicable disease, with their enabling and limiting factors at various implementation levels were evaluated. Sources of data: Keyword search was conducted in PubMed, Google Scholar, Embase, Medline, Science Direct, WHO and CDC online publication database. Using OCEBM as review criteria, 105 English-language articles, with ten bottom-up, non-pharmaceutical prevention measures, published between January 2000 and May 2020 were identified and examined. Areas of Agreement: Evidence-guided behavioural measures against COVID-19 transmission for global at-risk communities are identified. Area of Concern: Strong evidence-based systematic behavioural studies for COVID-19 prevention are lacking. Growing points: Very limited research publications are available for non-pharmaceutical interventions to facilitate pandemic response. Areas timely for research: Research with strong implementation feasibility that targets resource-poor settings with low baseline Health-EDRM capacity is urgently need. Uncertainties in disease epidemiology, treatment and management in biological hazards have often urged policy makers and community health protection to revisit prevention approaches to maximise infection control and protection. The COVID-19 pandemic, a disease caused by novel coronavirus SARS-CoV-2, has pushed global governments and communities to revisit the appropriate non-pharmaceutical, health prevention measures in response to this unexpected virus outbreak 1 . The World Health Organisation (WHO) health emergency and disaster risk management (health-EDRM) framework refers to the structured analysis and management of health risks brought upon by emergencies and disasters. The framework focuses on prevention and risk mitigation through hazard and vulnerability reduction, preparedness, response and recovery measures 2 , and further calls attention to the significance of community involvement to counteract the potential negative impacts of hazardous events such as infectious disease outbreaks 2 . COVID-19 is defined as a biological hazard under the health-EDRM disaster classification 3 . While there is evidence for potential COVID-19 droplet transmission 4 , the WHO has suggested that airborne transmission may only be possible in certain circumstances 4 . Further evidence is needed to categorise it as an airborne disease specifically, per the framework. Health-EDRM prevention measures can be classified into primary, secondary or tertiary levels 5 . Primary prevention mitigates the occurrence of illness through an emphasis on health promotion and education aimed at behavioural modification 6 ; secondary prevention involves screening and infection identification; and tertiary prevention focuses on treatment. In the context of COVID-19, both secondary and tertiary preventive measures are complicated due to the high incidence of asymptomatic patients 7 ; the lack of consensus and availability of specific treatment or vaccine 8 ; and the added stress on the health system during a pandemic. Primary prevention that focuses on protecting an individual from contracting an infection 9 is thus the most practical option. A comprehensive disaster management cycle (prevention, mitigation, preparedness, response and recovery) encompasses both top-down and bottom-up measures 10, 11 . Top-down measures require well-driven bottom-up initiatives to successfully achieve primary prevention and effectively modify community behaviours 12 . Based on the health-EDRM framework, which emphases the impact of context on efficacy of measure practices 3 , this paper examines available published evidence on primary prevention measures that might be adopted at the personal, household and community level for droplet-The literature was categorised according to the Oxford Centre for Evidence-Based Medicine (OCEBM) Levels of Evidence ( Fig. 1) 13 , which systemises strength of evidence into levels, based on process of study design and methodology. Individual RCT (with narrow Confidence Interval) 1C All or none 2A Individual cohort study (including low quality RCT; e.g., <80% follow-up) 2C "Outcomes" Research; Ecological studies 3A SR (with homogeneity) of case-control studies 3B Individual Case-Control Study 4 Case-series (and poor quality cohort and case-control studies) 5 Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles" The search identified 105 relevant publications, all of which were reviewed and included in the results analysis. The search identified ten bottom-up, non-pharmaceutical, primary prevention measures, based on the health-EDRM framework. The review of evidence is disaggregated into the ten prevention measures. Six personal protective practices (engage in regular handwashing, wear face mask, avoid touching the face, cover mouth and nose when coughing and sneezing, bring personal utensils for when dining out, closing toilet cover when flushing), two household practices (disinfect household surfaces, avoid sharing cutlery) and two community practices (avoid crowds and mass gatherings, avoid travel) were identified. Tables 1a, 1b and 1c highlight the potential health risk; desired behavioural changes; potential health co-benefits; enabling and limiting factors; and strength of evidence available in published literature with regards to these measures. 13 . Details each utilised reference can be found in Appendix 1. Quantity of evidence varies between each of ten measures reviewed, with handwashing and face mask practices having the most published resources available. Only a few systematic and longitudinal studies could be identified. Available evidence consists of predominantly level IV and V studies, and mainly of cross-sectional studies, guidelines and expert opinion. 5 4, 14 . • Droplets can persist on hands and other surfaces 15 . • Droplets may be transferred if hands are not disinfected. • Respiratory droplets from other individuals and hand-toface contacts can result in droplet intake through the nose and mouth 16, 17, 4 . • Viruses have the potential to survive in the respiratory tract 18 . The virus may also enter through ocular means, although studies focusing specifically on COVID-19 are limited 19 . • COVID-19 has an incubation period of as long as 19 days 20 ; asymptomatic or mildly symptomatic individuals may spread the virus through coughing or sneezing. • In 2010, WHO stated that where there is improper mask usage, risk may increase 21 . • Recent research has suggested that nasal carriage 22 and ocular entry 19 are key alternative routes to oral entry into the respiratory tract for COVID- 19 . • It has been demonstrated that COVID-19 can be detected on surfaces of plastic, stainless steel, copper and cardboard for up to 72 hours 15 after contamination. Hand-to-face contact following contact of public surfaces may pose a risk. • Wash hands with soap 23, 24, 25, 26, 27, 28, 20, 29 for a minimum of 20 seconds using a step-by-step guideline such as the WHO healthcare-based 11-step guideline 30 . • Wash hands before eating, after bathroom usage, after mask removal et cetera. • Practice alternative handwashing routines as long as they maintain the core principle of ensuring that the entire surface area of the hands is scrubbed 31 . • Ensure commonly missed areas are washed, such as the thumbs and fingertips 32, 33, 34, 35 . • Wear surgical face masks 36, 37, 38, 39, 28, 20, 29 to create a physical barrier preventing the spread or intake of the virus-containing respiratory droplet (which are released by coughing or sneezing) through facial openings 40 . • Wear face masks to minimise the touching of the nose and mouth as these can serve as transmission routes for COVID-19 16, 41, 17, 4 . • Use face masks correctly to ensure the best overall effectiveness, including one-time usage; limiting usage to one day; and avoid touching the surface to minimise risk of self-contamination 42, 43 . • Avoid touching the face to minimise the risk of COVID-19 contact through the body's main entry points for transmittable conditions 44, 36, 27, 28, 29 : the mouth, the eyes and the nose. • Exercise increased awareness of this unwanted practice to minimise the risk of infection, as self-touching of the face may be spontaneous 45, 46 . • Prevention of other contact-transmissible diseases such as influenza 47, 48 , to some extent, diarrhoea 49, 50 and eye infections 51 . • Potential for reduced infection transmission in community and household 52 . • Protection against other microbes transmitted by respiratory droplets through the nose, mouth or eyes 19, 22 . • Protection from air pollutants and other air particles 53, 54 , which could cause other respiratory conditions 55 such as asthma and lung cancer 56, 57 . • Minimises contracting diseases with similar transmission pathways such as influenza 58, 44 . • Reduce risk of transferring bacterial pathogens found on hands 59 . • Availability and affordability of running and sufficient water, soap and alcohol-based rubs. • Access to effective face masks. • Information about the correct use of face masks, • Alcohol-based formulas as alternative; efficacy in killing enveloped viruses has been demonstrated 60 . • Use of ash and mud as an alternative in areas where there is no access to soap or alcoholbased rubs, Although these carry potential antimicrobial properties 61 , their efficacy in counteracting viral infections is not wellevidenced 62 . • In areas with scarce running water, sharing and reusing of water or water-container elevates risk of transmission through droplets 63 . • For those who cannot access surgical face masks, due to affordability, availability or otherwise, homemade masks 64 accompanied with the same hygienic measures can be considered 65 . • Where face-touching is necessary or difficult to control, for example in infants or children, handwashing will be a more effective prevention measure. • Published evidence showed handwashing is a core community prevention measure for COVID-19 transmission. • Handwashing communities display lower risks of developing transmittable diseases when compared to their non-handwashing counterparts, in both rural 61 44 . Research suggests that such pathogen-bearing droplets can travel up to 7-8 metres 76 . • There is a high possibility of COVID-19 transmission through saliva droplets 77, 78 in instances where public utensils are not sufficiently disinfected 79, 80 . • There is growing evidence of COVID-19 being present in stool after clearance through the respiratory tract 81, 82 . • Virus particles present in stool can be transmitted through toilet plume generated after flushing 83, 84 , especially if the toilet is unclosed. • Cough/sneeze into tissue paper that is disposed immediately. • Replace mask after a major sneeze. • Cough or sneeze into elbow or shirt if mask or tissue is unavailable 85 . • These practices 36, 37, 38, 25, 20, 29 minimise droplet landings on the hands, which are most likely to come into contact with oneself and other surfaces. Hands should be disinfected after coughing or sneezing. • Avoid food consumption with public utensils, or utensils that have not been confirmed to be disinfected. • Use personal utensils 86, 29, 87 that have been appropriately disinfected for food consumption. • Cover toilets prior to flushing, both at home and in public. • Avoid public toilets during such a pandemic, especially those with toilets lacking lids 88 . • Minimising risk of other droplet-transmittable diseases 44 . • Prevention of other diseases that are transmitted through saliva 58 . • Improved household hygiene and protection from pathogens present in stool, such as bacterial or norovirus infections causing gastroenteritis 84 . • Access to masks and tissue. • Adequate mobility and reaction to raise elbow or tissue to the face. • Access to personal reusable or singleuse utensils. • Access to a toilet with a functional lid. • People with limited mobility, such as the elderly 89,90 , may not be able to react in time. The alternative is to maximise mask wearing as a permanent physical barrier. • May not be applicable to contexts where eating with hands is the tradition. Handwashing should be the primary preventive measure in these contexts. • Where personal utensils are not available, single-use utensils can be considered, although there are environmental implications of disposable utensils 91, 92 . • Another study has suggested that due to space between the lid and the toilet bowl, shutting the lid may not impede emissions entirely 93 . • For households lacking lidded toilets, other protective measures include regular cleaning; wearing a face amsk during toilet usage; and avoiding sharing toilets. 8 • There is strong evidence supporting the transmission of COVID-19 through respiratory droplets, which can be expelled in sneezing and coughing 94, 95, 27 . • Some evidence indicates that wearing a mask redirects coughed particles to a less harmful direction 39 -similar outcome may be inferred for tissue or elbow blockage although it may not be as effective. • There is lacking evidence on how each of the behavioural changes contribute to risk reduction for COVID-19 specifically. • There is no specific evidence of COVID-19 transmitting through public cutlery. • Limited evidence suggesting restaurants or caterers fail to properly disinfect their reusable cutlery. • Although this has not been directly confirmed, there is growing evidence that COVID-19 may be present in stool. • There is evidence that toilet plumes ascend when toilets remain open. • This measure has been suggested by authorities in places such as Hong Kong 28 . Avoid Sharing Utensils • COVID-19 has varying stability on different household surfaces, including metal, wood, glass, plastic, paper and steel 96 . • Personal belongings such as mobile phones and laptops have been shown to carry a high load of bacteria 97,98 due to inadequate cleansing and lots of hand-contact. The same may apply for virus particles. • Studies have previously demonstrated cutlery sharing practices as a risk for oral transmission 99 . • Due to the high possibility of COVID-19 transmission through saliva droplets 77, 78 , it may pose similar risk. • There is additional unknown risk due to potential for asymptomatic transmission 20 . • Disinfect households regularly 37, 24, 25, 27, 28, 29 , especially frequently touched objects and surfaces 43 , with biocidal agents such as 62-71% ethanol, 0.1% sodium hypochlorite or 0.5% hydrogen peroxide 75 . • Use a dilution of 1:50 bleach for general household disinfecting of flooring and doors 75 . • Disinfect smaller objects, such as keys, or surfaces that come in contact with the face and mouth, such as mobile phones, with 62-71% ethanol or alcohol wipes instead 75 , due to potential hazards from bleach 100 . • Avoid sharing of utensils or serving food from a communal dish with used utensils. • Use designated serving-utensils to prevent saliva-based droplet transmission. • Maintain hygiene practices, such as adequate cleaning of all utensils. • Improved general household hygiene, such as mould reduction 101, 102 . • Opportunity for mild physical activity to compensate for lack of outdoor exercise during COVID-19 social isolation. • Reduced risk of other saliva-transmitted bacteria while utensilsharing 86 . • Reduced risk of dental caries transmission 103 . • Access to proper disinfectants. • Knowledge on safe use and storage of disinfectants. • Availability of serving utensils. • Cultural appropriateness, such as when seating in settings where such sharing is expected. Factor(s) and/or Alternative(s) • Where resources are limited, households should use the best disinfectant possible, reduce the frequency of disinfection, or target frequently touched surfaces such as door handles. • Where appropriate, hand-consumption after adequate handwashing may be considered to avoid utensil-sharing. Proper handwashing practices must be observed. 9 75 . • Evidence on the effectiveness against COVID-19 specifically is lacking. • Given its transmission through droplets 14 , and persistence in saliva 77 , this prevention measure should be considered good practice. • This measure was recommended by the CDC during the 2003 SARS outbreak 29 . • There is no study on the impact of utensil-sharing on COVID-19 specifically. • Studies have noted potential spread of H. Pylori via shared chopsticks 87 . • Crowded areas with unknown people are considered high-risk due to risk of droplet transmission and infection through contaminated surfaces. • Talking can potentially result in respiratory infectious disease transmission 104 . • Possibility of transmission by asymptomatic carriers within a crowd increases risk 105 . • Travelling to areas with confirmed cases will increase an individual's risk of potential exposure to COVID-19. • The stability of the virus on surfaces 15 , the potential prevalence of asymptomatic carriers 105 , the difficulty and lack of distancing 106 , shared toilets and risk of toilet plume 82 , and uncertain travel history of others make environments such as trains and aeroplanes challenging in terms of protection and high risk in terms of COVID-19 transmission. • Observe social distancing measures 4, 14, 37, 74, 27, 28, 20, 29, 107 . • A separation of 1 metre is the minimum as recommended by the WHO 36 . Although most droplets may not travel across this distance, novel studies exploring the influence of aerodynamics 108 as well as the potential for sneezes to travel up to 8 meters 76 have led to the recommendation that possible distancing should be maintained wherever possible. • Avoid congregating and take precaution when in public areas such as parks, cinemas, restaurants. These areas should make face mask wearing mandatory, carry out temperature checks, limit the number of people in attendance, and practice distancing of people. • Avoid travelling to areas with confirmed cases, which are of significant risk 28, 20, 29 . • Take all necessary personal protective measures such as wearing of face masks, eye googles, disinfecting immediate area with alcohol-based solution and avoiding food sharing. • Implement (for authorities) appropriate protective measures such as mandatory temperature checks prior to travel and/or upon arrival, reporting the travel and medical history of each traveller, and distancing requirements on transport. • Reduced outdoor pollution due to minimised outdoor human activity 109, 110 . • Lower exposure to outdoor air pollution which causes respiratory illnesses such as lung cancer and contributes to mortality 111, 55 . • Reduction of cross-border transmission 107 . • Improved general hygiene on transport such as trains or aeroplanes • Environmental benefit from reduced air-travel carbon footprint 112 . • Ability to avoid crowded areas as permissible by population density, occupation, religion or culture. • Ability to make decisions on when or how to travel. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. • Crowded areas may not be avoidable due to occupation, religious belief or otherwise. Where gathering is necessary, individuals should take personal responsibility to wear masks, keep hands clean, and maintain maximum distance from others. • Access to facemasks, goggles or alcohol-based solution for personal protection during travel. • The necessity of travel, for personal or professional reasons, such as pilots and the cabin crew. • Studies on influenza and COVID-19 113 indicate a potential role of mass gathering reduction in limiting transmission 114 , though studies are limited and not yet conclusive. • There are also studies on the elevated transmission of other viruses as a result of mass gatherings 115, 116, 117 . • The proximity and contact with individuals heighten the evidenced risk of taking in potential respiratory droplets containing COVID-19 from others. • There is no clear evidence regarding increased risk from aeroplane travel specifically. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. Evidence relating to ten health-EDRM behavioural measures for primary prevention against droplet-borne biological hazards were identified and reviewed. At the time of writing, there is an outstanding question as to whether COVID-19 is transmitted through droplet or aerosol in the community. The information referenced here is based on best available evidence, and will need to be updated as new studies and guidelines are published, and the understanding of the scientific community is enhanced. Although direct evidence on the efficacy of prevention measures against COVID-19 specifically is lacking due to the novelty of the disease, five behavioural measures were identified: regular handwashing; wearing of face masks; avoidance of face touching; covering during sneezing or coughing; and household disinfecting were identified. Five other potential behavioural measures were also identified through logical deductions from potential behavioural risks associated with transmission of diseases similar to COVID-19 75 . Utensilrelated practices, in particular, were heavily limited in evidence to support their efficacy against viral infections. The efficacy and success of the ten bottom-up primary prevention measures reviewed here are subject to specific enabling and limiting determinants, ranging from demographic (e.g. age, gender, education), socio-cultural, economic (e.g. financial accessibility to commodities), and knowledge (e.g. understanding of risk, equipment use). The viability and efficacy of each measure may be limited by determinants and constraints in different contexts. Resource-deprived areas may face constraints and reduced effectiveness of implementation, especially for measures that require preventive commodities such as face masks and household disinfectants. As such, special attention should be given to rural settings, informal settlements, and resource-deficit contexts where access to information and resources such as clean water supply are often limited 119, 120 , and sanitation facilities are lacking 121 . For hygiene measures, different alternatives should be promoted and their relative scientific merits should be evaluated, such as the use of ash as an alternative to soap for handwashing 62 , or the efficacy of handwashing with alcohol sanitiser, which has been demonstrated in previously-published studies for H1N1 122 and noroviruses 123 but not yet for COVID-19. Meanwhile, for measures that have no direct alternatives available, it is important for authorities and policymakers to understand the capacity limitations of certain target groups, and provide additional support or put in place other preventive measures. In cases where material resources are scarce, the measures of awareness on sneezing and coughing etiquette as well as avoiding hand-to-face contact are the most convenient to adopt as they require little to no commodities. However, it should be well-noted that these measures are likely the most challenging in compliance and enforceability, as they rely on the modification of frequent and natural human behaviours whose modifications would require awareness and practice 45, 46 . Furthermore, these can be challenging to implement in target groups with less capacity for health literacy and translation of education into practice, such as infants and elderly suffering from dementia. Cultural patterns can be associated with behavioural intentions, in the case of avoiding . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . utensil-sharing during meals, enforcing change may be conflicted with cultural and traditional norms in Asia and certain European communities 124 . Of the enabling factors documented for each proposed measure, shared enablers can be identified: accessibility and affordability of resources; related knowledge, awareness and understanding of risk; and associated top-down policy facilitation. Majority of personal and household practices heavily rely on access to resources, such as adequate water and soap supply for regular handwashing, quality face masks and household-disinfectants. Various theories of the 'Knowledge, Attitudes, Practices' model have assumed that individual knowledge enhancement will lead to positive behavioural changes 118 . Health measures targeting mask-wearing might aim to enhance (1) the individual's risk perception, knowledge and awareness on protection effectiveness of masks, and how to properly wear a mask so that the prevention is most effective; (2) an individual or community's attitude towards the practice of mask-wearing and encouraging compliance in the West, as studies demonstrate a relatively greater social stigmatisation towards mask-wearing amongst Westerners than East Asians 125 , and (3) normalising the practice of habitual mask-wearing. Such a conceptual framework should be utilized in the implementation of the health initiatives. In terms of overarching knowledge, health education on symptomidentification is also important, as seen on government platforms such as the CDC 37 . Enhancing health-seeking behaviour of potential carriers is critical to promoting a rapid response for quarantine or hospitalisation. At the individual level, behavioural changes have different sustainability potentials and limitations. Measures can also result in unintended consequences, such as the improper disposal of face masks 126 and the incorrect use of household disinfectants 127 should be carefully monitored to maximise impact while minimising further health and safety risks. Top-down policy facilitation and strengthening of infrastructure will be essential for effective implementation. Top-down efforts in resource provision, such as the distribution of quality masks to all citizens by the government or similar authority 128 , enhance personal and household capacities to mitigate infection risks. On compliance, the effectiveness of community practices such as crowd and travel avoidance are highly dependent on the needs and circumstances of an individual and a community. More assertive top-down policies such as travel bans and social distancing rules may drive bottom-up initiatives within communities under legal deterrence 129 . However, in order to ensure population-level compliance to recommendations that have wideranging socioeconomic impact and involve more than a day-to-day behavioural change, careful risk and information communication is required, which takes in to consideration practical, legal and ethical aspects. The strength of evidence available for each practice is dependent on multiple factors. In the case of a novel or emerging disease such as COVID-19, available evidence can be related specifically to the disease and pandemic, but some findings are deduced from studies on other similar viral infections and transmittable conditions, such as SARS or Influenza. Many interventions . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . proposed by health authorities are not based on rigorous population-based longitudinal studies. While handwashing is well-regarded as a core measure by global and national public health agencies such as the WHO 36 and CDC 37 the chemical properties of eliminating enveloped viruses is understood 60, 38 , specific studies on the practice's efficacy and impact on COVID-19 transmission are lacking. Due to the uncertainties of disease pathology and epidemiology, effectiveness of behavioural measures against COVID-19 are far from conclusive. Other uncertainties are also reported on virus surface stability 15 and if the efficacy of disinfectants against surface-stable viruses might vary with COVID-19 75 . Similar deductive evidence approaches from studies on other viruses have been utilised to judge the efficacy of face masks or the shutting of toilet lids 84, 83 . Although published evidence suggested individual measures such as covering coughs and sneezes to be helpful against droplet transmissions 14 , further research is needed to understand the true efficacy of coverings such as masks, tissues or elbows as an adequate preventive measure against COVID-19. Given the rapid knowledge advancement and research updates related to COVID-19, further study updates will be warranted to identify the most appropriate behavioural measures to support bottom up biological hazard responses. Cost-effectiveness of the measures, their impact sustainability, co-benefits and risk implications on other sectors should also be examined and evaluated. Standardised studies across different contexts should be enhanced, for example conducting tests on the efficacy of different disinfectants or soaps under a standardised protocol. Such studies would increase evidence on individual and comparative efficacy. The limitations in this review include language (English language only); database inclusion (grey literature not included); online accessibility of the article; and missed keywords. Publications documenting the experiences of traditional, non-English-speaking, rural communities during the COVID-19 pandemic might not be included in this review. Further research should review the measures' efficacy in different contexts and make comparisons with their alternative measures. Specifically, alternative preventive measures that can be practiced in resource-poor, developing communities, whose health systems and economies generally suffer the greatest impact during pandemics are urgently needed. Increased understanding of how to effectively mitigate against biological hazards such as COVID-19 in various contexts will help communities prepare for future outbreaks and build disaster resilience in line with the recommendations from the health-EDRM framework. Despite the constraints, this review has nevertheless identified common, relevant behavioural measures supported by best available evidence for the design and implementation of health policies that prevent droplet-borne biological hazards. Many of the measures recommended by authorities during the pandemic are based on best practice available rather than best available evidence. The possibility of conducting large cohort or randomised controlled studies is often complicated, and rather infeasible during a pandemic, as noted for face masks 130, 131 . Further studies are needed to understand the efficacy of frequently proposed measures for transmission . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . risk reduction. Nonetheless, each of the measures identified has scientific basis in mitigating the risk of droplet transmission 14 , either through personal measures such as handwashing, or community-based measures which aim to reduce person-to-person contact. It is important to explore the efficacy of alternatives, notably for transmission prevention and risk communication in low-resources or developing contexts where the capacity of the health system to mitigate and manage emergency events outbreaks are weak. For example, while face masks are understudied, the scientific study of cloth masks as an alternative is severely limited 65 , although recommended by the CDC 132 . Such alternative studies should expand to consider different cultures and contexts where different varieties of disinfectants, face masks and utensils may be used. There is also potential for comparative effectiveness studies to explore measures that provide the greatest transmission risk reduction at the lowest transaction cost to the individual and community and should thus be prioritised in low-resource contexts 133 . During the outbreak of a novel transmissible disease such as COVID-19, primary prevention is the strongest and most effective line of defence to reduce health risks when there is an absence of effective treatment or vaccine. COVID-19 is and will be subjected to ongoing research and scrutiny by global scientists, health professionals and policy makers. While research gaps remain on the efficacy of various health-EDRM prevention measures in risk reduction and transmission control of COVID-19, suboptimal scientific evidence does not negate the potential benefits arising from good hygiene practices, especially where the likelihood for negative outcome is minimal. Despite the lack of rigorous scientific evidence, the best available practice-based health education content, effective means of information dissemination, equitable access to resources, and monitoring of unintended consequences of the promoted measures, such as environmental pollution due to poor waste management, will be essential. A top-down approach should be multi-sectorial, bringing in policy makers with clinical, public health, environmental, and community management expertise to develop a coordinated and comprehensive approach in a globalised world. The authors declare no conflicts of interest. The study is fully funded by the CCOUC-University of Oxford research fund (2019-2023). . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. • Findings suggest that both significantly reduced the bacterial colony (with no significant difference between the two) but that the 3-step guidelines had higher compliance. Quantity of steps are not of great concern as long as areas are covered. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. • Environmental burden of disease and association to air pollution is a main concern in the fast-developing areas of India. • Households exposed to high vehicle-caused pollution presented with greater prevalence of respiratory diseases for example. 58 Saliva . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. • While a homemade mask also results in a decrease in number of microorganisms expelled by volunteers, a homemade mask is significantly less effective than surgical masks and should only be a last resort for droplet transmission prevention. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. April 2020 B Level 1b: A randomised controlled trial to compare the effectiveness of surgical and cotton masks in filtering SARS-CoV-2 • Both surgical and cotton masks are potentially ineffective in the prevention of SARS-CoV-2 from patient coughs to the environment and external mask surface. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. • Health hazards such as premature deaths and paediatric asthma associated with air pollution have been minimised as a result of reduced activity in COVID-19. • There are potential health benefits from reduced air pollutant emissions as a result of decreased economic activity during the pandemic. 110 COVID-19 as a Factor Influencing Air Pollution? 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