Work-related infections Part 2 Prevention and control strategies

 1 Immunology and Microbiology Section, National Institute for Occupational Health, National Health Laboratory Service, Johannesburg, South Africa

2 Department of Clinical Microbiology and Infectious Diseases, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Johannesburg, South Africa

3 Working Group on Occupational Infectious Agents, International Commission for Occupational Health (ICOH)

 

Correspondence: Dr Tanusha Singh, National Institute for Occupational Health PO Box 4788, Johannesburg, 2000, South Africa. e-mail: tanusha.singh@nioh.nhls.ac.za

 

ABSTRACT

Infectious diseases are a major concern in the workplace, be they associated with work processes or community-acquired infections spread in the workplace; and their prevention and management require the implementation of robust prevention and control strategies. The transmission of infectious agents is a weak link in the chain of infection and one where intervention may have the greatest chance of breaking the cycle of infection. Consideration of the mode of transmission is a critical factor in prevention programmes. Adequate control measures for elimination or containment of the infectious source, followed by early detection of disease and promotion of best practices, complemented by appropriate training, are fundamental to managing hazardous biological exposures in the workplace.

 

Keywords: work-related, occupational infectious disease, infection prevention and control, transmission, hazardous
biological agents

 

INTRODUCTION

The risk of contracting infections from exposure to infectious agents, and their transmission routes by industry or sector in the workplace,1-5 have been described in detail in Part I of this series.6 The transmissible agents causing or aggravating disease outcomes include bacteria, fungi, parasites, and viruses, and toxins produced by these agents (Table 1).3,7,8 The exposure can be either intentional through handling of microorganisms (e.g. laboratories, pharmaceutical industry), or inadvertent from work processes or the environment (e.g. outdoors or water-damaged buildings).5,9 Work-related infectious diseases may lead to high mortality rates in the workforce,5 estimated at 320 000 deaths of employees per annum globally.8 Apart from the high mortality rate, ooccupational infectious diseases (OIDs) lead to morbidity, low productivity and absenteeism, and thus have a negative impact on the economy. OIDs are often under-reported,5 possibly due to workers fearing job loss, no clear link between work and the disease (e.g. overlap with community-acquired infections), and infections inadequately recognised as being work-related or regarded as non-threatening (e.g. influenza).5 However, reporting is important as it aids in understanding the magnitude of the problem and will indicate the required prevention and control measures.5,10

The industries most commonly associated with a high risk of infection amongst workers include healthcare, biotechnology, agriculture, forestry and fisheries, animal care, sewage or waste recycling, and general workplaces such as office buildings.5,9,11,12 Infection is frequently a result of multiple causes, such as human behaviour, economic constraints and system failures.10,13 Prevention of infectious disease transmission is of considerable public health importance8 but it remains a challenge across industries due to increased workloads, lack of awareness and communication, inadequate policies and poor implementation and compliance, as well as limited financial and human resources.9,14,15

This paper is the second of a three-part series on work-related infectious diseases and will focus on the basic principles of prevention and control strategies. Although the mitigation of exposure is highly dependent on the risk assessment outcome, the latter will be addressed in Part 3 of the series. 

 

PREVENTION AND CONTROL OF INFECTIOUS AGENTS

Infection control is not a stand-alone concept, but an integral part of the occupational health and safety programme, and should therefore be aligned to legislated requirements such as the Occupational Health and Safety Act (No. 85 of 1993)16 and the Mine Health and Safety Act (No. 29 of 1996).17 Workplaces should have a biorisk management plan describing how employees are protected from infections in the workplace, which should include the nature of hazards and the risks involved, including rating, control measures and a schedule for monitoring and evaluation.4,18,19 Preventing workplace infections should also focus on transforming the health and safety culture of workers (perceptions, values and beliefs) to be aligned with the organisation’s occupational health and safety (OHS) management system and the relevant regulations. The approach by different workplaces to mitigate and control infectious exposure will depend on how risk tolerant or averse the company is. However, it should follow the required containment measures that are stipulated in the Hazardous Biological Agents Regulations and the known hierarchy of controls, where relevant.8,20-22
In addition, different risks require different approaches towards prevention and controlling the exposure. The transmission of infectious agents is a weak link in the chain of infection and one where intervention may have the greatest chance of breaking the infection cycle. Therefore, the mitigation strategy, which includes the hierarchy of infection control, should target the transmission link through elimination or substitution of potential exposure where applicable, engineering and environmental controls, administrative controls, particularly immunisation if available, and personal protection (Figure 1).1,23,24

 

PREVENTION OF AIRBORNE INFECTIONS

Airborne transmission presents a risk to workers, especially in hospitals, because bio-aerosols are easily spread from infected, undiagnosed and poorly-treated patients.9,14 Occupational disease caused by bio-aerosols in Korea is rated the third most common after pneumoconiosis and hearing loss.11,12 In South Africa, the annual incidence of TB was 860 per 100 000 in 2013, and healthcare workers (HCWs) were at a five-fold greater risk of developing drug-resistant TB than the general population.25 The transmission of airborne infections is through droplet (big particles) and airborne (small particles) routes9 and the source of exposure can be both human and non-human (inanimate).9,23 The selection of respirator must be carefully considered depending on the infectious agents, if known, and the level of protection required.26 Paper or surgical masks or tissues should be provided to patients to reduce transmission. These masks are not designed to protect the user.4,27

 

PREVENTION OF BLOODBORNE INFECTIONS

All blood should be considered to be potentially infectious with bloodborne pathogens (e.g. HIV, hepatitis B and C, Ebola and other viral haemorrhagic fevers (VHF) and even malaria). Hepatitis B is the most common bloodborne pathogen and is easily transmitted, although it is easily prevented through immunisation.16 The highest risk exposures can occur through needle sticks, sharps injuries, or splashes to a worker’s mucous membranes.6,15,16 The effective way to prevent exposure to bloodborne infections is to use safety-engineered devices such as shielded scalpels, retractable or blunt needles, and leak-resistant specimen bottles.2,28 Sharps containers must be readily available in all work areas for proper disposal when two thirds full, should not be stored on the floor,3,4 and should be separated from biomedical waste. Routine practices such as hand washing, safe work practices, hepatitis B immun-isation, and the use of PPE (e.g. gloves, eye protection, head protection and gowns) should be enforced when handling blood or other body fluids. In most healthcare settings, post exposure antiretroviral prophylaxis has been strongly advocated for HIV; and immunisation plus human immune globulin, if indicated, for hepatitis B.3,8,21 There is currently no prophylaxis for hepatitis C and prevention for transmission is by strictly adhering to standard precautions, as with other bloodborne pathogens.3

 

PREVENTION OF CONTACT INFECTION

Microorganisms (e.g. vancomycin resistant enterococcus (VRE) and Methicillin-resistant Staphylococcus aureus (MRSA) can be transmitted directly or indirectly from human hands or surfaces to other persons through contact or can further contaminate other surfaces during movement of people, air and objects. Hand washing with soap and water is the simplest, yet the most effective, procedure to reduce the spread of infectious agents.2,4,29 Alcohol-based hand rubs can also be used; however, they are not effective against all organisms, such as Clostridium difficile. Contaminated surfaces should be regularly decontaminated with appropriate disinfectants,6 and blood spills should be clearly demarcated and appropriately treated with disinfectant.4 Employees with diarrhoeal symptoms from foodborne outbreaks should not return to work until asymptomatic (usually 2-3 days).

Diseases such as Scabies (Sarcoptes scabiei) and leptospirosis are spread by prolonged skin contact with an infected person or animal/water, respectively. The latter affects workers in farms (zoonotic), abattoirs, and sewage plants, as well as soldiers, and can be prevented by adopting general hygienic measures, using protective clothing and footwear, rodent control, and immunisation of livestock. There is currently no leptospirosis vaccine available for human application.30

 

PREVENTION OF FOOD AND WATERBORNE
INFECTIONS

Typhoid fever caused by Salmonella typhi is a common occupational infection and has been reported in laboratory staff as well as sewer workers and HCWs. Free-living amoebae (FLA), e.g. Acanthamoeba and Naeglaria, are known pathogens to humans and act as reservoirs of pathogenic bacteria (Acinetobacter, Aeromonas, Alcaligenes, Bacillus cereus, E.coli, Legionella, Mycobacterium, Pseudomonas aeruginosa). Resistance of the FLA to biocidal (chlorine) treatment plays a major role in disease transmission.31,32

Foodborne diseases can be avoided by following the necessary food and drink precautions, good hand hygiene, sanitation in food preparatory areas and dining areas, proper food storage, frequent inspections, and immunisation. Workers should be tested and immunised for hepatitis A, depending on the risk of exposure.3,12 Caterers should also be trained on basic food hygiene and the importance of immediate reporting of foodborne outbreaks to authorities, which will aid in surveillance and control of foodborne diseases,2,10 and identify shortcomings of infection control measures.10

 

PREVENTION OF VECTORBORNE AND
ZOONOTIC INFECTIONS

While occupational zoonotic diseases are rare, some pose a significant health risk for workers in certain occupations, such as animal handlers, abattoir workers, agricultural workers, laboratory staff, HCWs and researchers. Fungal infection with Microsporum canis, for example, has been reported in animal trainers and keepers.11 There is a lack of information on work-related infectious diseases; however, Australia (2003) reported prevalences for Q fever (65.9%), leptospirosis (13.4%), Brucellosis (3.5%) and Psittacosis (17.7%).31 Malaria caused by Plasmodium falciparum can be prevented by avoiding mosquito bites and using prophylactic anti-malarial medication.3,12 Prevention measures for zoonotic diseases caused by campylobacter and hanta virus (also airborne) include hand hygiene and contact precaution for both agents as well as airborne precaution for hanta virus. Hand washing or alcohol hand rubbing is recommended after handling animals or faeces.4

 

HIERARCHY OF CONTROL

The key elements to control the transmission of infectious pathogens in order of effectiveness are summarised below and illustrated in Figure 1. The prevention and control framework for occupational infectious agents is not simplistic with sequential steps, as the intervention for certain agents is often immunisation or chemoprophylaxis, or even early treatment to prevent transmission. Therefore, the approach depends on the agent concerned, work processes among other determinants of transmission, and financial resources. In cases where controls are not practical for a particular agent, one must progress to the next pillar of control or apply a combination of controls.

 

Engineering and environmental controls

The most common strategies used to reduce exposure to infectious agents include mechanical ventilation, natural ventilation, high efficiency particulate arrestance (HEPA) filtration and ultraviolet germicidal irradiation (UVGI) devices, as well as engineering to isolate the hazard from the worker.2 Well-designed engineering controls can be highly effective in protecting workers and generally reduce the protective burden on the worker, providing higher level of protection.33 Poor design, poor installation and lack of maintenance of engineering controls reduces the effectiveness of UVGI devices, creating a false sense of security to workers, and can pose a risk by harbouring microbial agents.9 Engineering controls are generally costly and should be implemented based on priorities as identified in a risk assessment. Escombe and colleagues compared natural and mechanical ventilation in two hospitals and found the naturally ventilated hospital to have more than double the number of air changes per hour (ACH). Furthermore, patients in the naturally ventilated rooms were at a significantly lower risk of contracting TB, due to the increased ACH.34 Two open air hospitals in Haiti have recently been reported having reduced respiratory infections including TB.1,35 A few South African studies in healthcare facilities identifying airborne pathogens have shown the necessity of air quality monitoring to prevent contamination and infections, and to assess the effectiveness of engineering controls.14,36 The drawback with natural ventilation is that it is unpredictable and can pose security risks. Site assessments should therefore be conducted by a specialist in the field. Monitoring exposure for biological agents in the workplace is a legal requirement;16 therefore, hazardous agents should be monitored and controlled to minimise their dispersal.

 

Administrative controls

Controls to ensure safe working practices are developed to reduce exposure to infectious agents within a facility. To maximise the effectiveness of administrative controls, employees at all levels must be made aware of potential threats in their workplaces.1 Occupational health practitioners (OHPs) should be familiar with work-related infections so that they can contribute to the formulation of policies and programmes for infections affecting workers.12 Medical surveillance, where applicable, should be implemented in high risk occupations as a means of ensuring early diagnosis.19 Immunisation can be used effectively for controlling several infections, including those occupationally acquired.1

 

Education and training

General awareness and education are essential for assisting employees to understand potential exposure to infectious diseases, how they are transmitted, symptoms, prevention, and treatment, and how to control exposure.4,37 Workers must also be educated about working safely, reporting incidents promptly and accurately, and accessibility of relevant vaccines. Employees who have signs and symptoms of illness must be encouraged to stay home until their health has improved in order to limit transmission.4,12 A collaborative effort between Canada, the National Institute for Occupational Health (NIOH) and the Free State Department of Health, for HIV/TB prevention interventions, led to the development of a one-year certificate programme in occupational health and infection control.37 This programme will empower HCWs and management to maximise preventive interventions, and can be promoted in other industries.


Personal hygiene and decontamination

General hygiene procedures, including hand washing (~40-60 seconds),2,4,9,13 are critical in infection control in facilities. Hand sanitation (~20-30 seconds), using alcohol-based hand rubs, has also been proven to be cost-effective.13 However, it is not effective in killing some organisms, e.g. Clostridium difficile which requires deep cleaning with hydrogen peroxide (H2O2).38,39 Multi drug resistant organisms are also deactivated effectively by using H2O2 vapour.40 Contaminated hands must be washed with disinfectant/soap and water (i) before leaving the work area, (ii) before and after individual or animal contact and specimen handling, (iii) after handling blood and contaminated items, (iv) before eating and after using the bathroom, and (v) immediately after removing gloves. Surface areas and reusable instruments should be cleaned and decontaminated, using an appropriate and effective disinfectant.2

 

Personal protective equipment (PPE)

PPE is important in controlling the spread of infectious diseases at work by acting as a barrier against body contact with blood and body fluids or airborne diseases as described. It must be used as a secondary measure in conjunction with engineering and administrative controls. However, in some instances where engineering controls are impracticable, insufficient or malfunction, PPE can be used as the primary means of control. Workers must always wear PPE where there is potential exposure, including temporary exposure such as a spill cleanup.23 The employer must ensure adequate supplies, annual fit-testing and practical refresher training for workers who are required to use respiratory protective equipment.23,41

Respirators are often the only protection for the worker against the potential adverse health effects of infectious airborne contaminants, where the causative agent/s cannot be eliminated or sufficiently reduced. Whenever respirators are used, a facility-specific respiratory protection programme (RPP) needs to be developed, implemented and periodically evaluated.42,43 Contaminated protective clothing should be isolated, and agitation should be avoided to minimise aerosolisation of infectious agents.2 Protective eyewear and medical gloves are useful during procedures involving blood or body fluids.23 All PPE should be correctly donned (put on), and special care should be taken when doffing (removing) due to possible hazardous biological agent contamination from work procedures.

 

CONCLUSION

Against the backdrop of the high burden of disease in South Africa, greater efforts are required to upscale infection prevention and control to protect workers and reduce disease rates. If poorly controlled, work-related infectious diseases have the potential to cause epidemics with a high socio-economic impact. There is scientific evidence for effective prevention and control strategies that can be adopted. Occupational diseases can be prevented by health examinations and immunisation programmes; workplace environmental monitoring will also benefit workers. Management needs to ensure the availability of resources for implementation of infection control measures, especially for high risk groups, based on disease severity and the infectiousness of the agent.

 

LESSONS LEARNED

1. Transmission of infectious diseases is a challenge; monitoring and reporting is necessary for prevention

2. Data on the prevalence of occupational infectious diseases in South Africa are lacking; surveillance systems are needed

3. Natural ventilation is as effective as mechanical ventilation and is affordable

4. Infections can be prevented by early identification, isolation, personal hygiene and immunisation

5. The selected disinfectant must be appropriate for the target biological agent to effectively inactivate it

6. Resource allocation for infection control should be based on the risk of transmission and infectiousness of the agent

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