Elimination of biological hazards includes construction guidelines in hospitals, standard precautions, which must be applied to all patients at all times, additional (transmission-based) precautions which are specific to modes of transmission (airborne, droplet and contact), environmental cleaning, sterilization and disinfection of patient equipment (Manyele et al., 2008).
1. Construction guidelines in hospitals:
An infection control team member should participate on the planning team for any new hospital construction or renovation of existing facilities. The role of infection control in this process is to review and approve construction plans to ensure that they meet standards for minimizing nosocomial infections (Walker et al., 2007).
Considerations will usually include selection of the site of hospitals which should be away from overcrowded public areas especially for hospitals managing infectious diseases as TB, SARS, meningitis and pandemic influenza. Considerations also include proper ventilation, isolation room design, proper traffic flow and appropriate access to hand washing facilities (Lateef, 2009).
a. Ventilation:
Of all the possible engineering techniques that can be employed to control airborne pathogens, good ventilation is probably the most effective. Although most people are familiar with the general concept of ventilation, very few understand the principles on which it is based. The term ventilation should therefore only be applied to the supply of outside air to the room space (Crimi et al., 2005).
Dilution ventilation:
Most ventilation systems push large quantities of ‘clean’ outside air into occupied spaces so that any contaminants in the room space are diluted and flushed out to atmosphere. To function properly good mixing of the air in the room space is essential (McLarnon et al., 2006).
Laminar and displacement ventilation:
This is based mainly on directing airflows to displace the contaminated air so that it is ‘pushed’ out of the room space. In this way the contaminated air is continually being replaced by clean air. With this type of ventilation system it is undesirable to have any air mixing and so ‘laminar’ streams of air are often used. Such ventilation systems are frequently used in operating theatres and isolation rooms (Abdulsalam et al., 2010).
Pressure differences ventilation:
By controlling the airflows within a building it is possible to create ‘high’ and ‘low’ pressure regions. This can be used to great advantage in isolation rooms, which can be negatively pressurized space so that airborne pathogens are unable to escape. These negative pressures can be achieved by supplying less air to an isolation room than is extracted. It is recommended that a positively pressurized anteroom be placed between the corridor and the isolation room according to fire regulations (Crimi et al., 2005).
Natural ventilation:
Many hospital buildings, especially older facilities, rely heavily on natural ventilation. In many ways the natural ventilation of clinical spaces is a good solution. However, reliance solely on natural ventilation has a number of drawbacks such as ventilation rates will be variable and are greatly dependent on the outside climatic conditions. Also, Pathogens such as Aspergillus spp. which is widespread in the outdoor environment can easily enter ward spaces (McLarnon et al., 2006).
b. Room air cleaning devices:
There are a variety of room air cleaning devices currently available, incorporating technologies such as high efficiency particulate air (HEPA) filters and ultraviolet germicidal irradiation (UVGI) lamps. These devices are intended to be mounted within a room space and are designed to reduce the microbial level in the room air. They have the advantage that they are relatively cheap and can be strategically positioned to protect vulnerable patients and staff (Crutis, 2007).
High efficiency particulate air (HEPA) filters units:
HEPA filter units are readily available machines that can be used any where to provide clean air. These units are especially useful in settings that may have inadequate or no ventilation and limited funds for upgrades. HEPA filters exhibit very high efficiencies (i.e. 99.9 % efficient for particles 0.3µm in diameter). HEPA filter unit will provide cleaned air to dilute infectious particles and will also remove airborne particles. HEPA filter units are available in a variety of sizes and configurations. All consist primarily of pre-filter to remove coarser particles and thereby prolong the life of the HEPA filter, a fan to circulate the filtered into the room and controls, such as an on/off switch and fan speed control (Liao et al., 2008).
The most common types of units are portable, free standing and permanent devices. Ceiling-mounted and wall-mounted units are also available. Portable units have the advantage of greater flexibility and ease of installation and service (Eckmanns et al., 2006).
Ultra-violet (UV) germicidal irradiation:
The germicidal properties of UV light have been known about for many years; in the pre-antibiotic era. UV lamps were used extensively in tuberculosis (TB) wards to control the spread of infection, but with the development of anti-bacterial drugs and, in some countries the introduction of vaccination against TB, UV air disinfection fell out of favour. However, in recent years, with the global rise in TB, there has been renewed interest in its use as an infection control measure and several research programmes have been initiated in this field (Kujundzic et al., 2006).
The activation spectrum peaks in the range 260 to 270 nm is similar to the absorption spectrum of nucleic acids, thus deoxyribonucleic acid (DNA) is the main target. UV light at this wave length is absorbed by nucleic acids with the formation of pyrimidine dimers, resulting in damage to the DNA of the micro-organism which is lethal. Conventional low and medium pressure mercury discharge UV lamps have a strong spectral emission at 253.7 nm, close to the peak of the action spectrum and can be used as an effective bactericidal agent (Rudnick and First, 2007).
C. Isolation room design:
The interest in the use of airborne isolation rooms has increased due to the occurrence of new emerging diseases such as severe acute respiratory syndrome (SARS), avian influenza and multi-drug resistant tuberculosis (MDR-TB). The recognition of the possibility of pandemic outbreaks of influenza has required authorities to put in place “emergency planning” for dealing with infected patients that may require isolation (Walker et al., 2007).
Isolation rooms can be used to limit the spread of small-particle aerosols, which may play a role in all isolated diseases. Mechanically ventilated isolation rooms can be classified in to standard, source and protective isolation room according to the ventilation pressure as shown in table (5) (Hoffman et al., 2004).
Isolation rooms should have minimum air-change rates of 6 air changes an hour (ach) for the protection of staff and visitors in the room. If possible, this should be increased to the 12 ach recommended as a minimum by the American institute of architects. The room airflow pattern should be designed to provide HCWs or visitors with clean air (Lateef, 2009).
d. Traffic flow:
Distinction can be made between high-traffic and low-traffic areas. A hospital with well-defined areas for specific activities can be described using flowcharts depicting the flow of in or outpatients, visitors and staff. Building or rebuilding a hospital requires consideration of all physical movements and communications and where contamination may occur (Manyele et al., 2008).
e. Architectural segregation:
It is useful to stratify patient care areas by risk of the patient population for acquisition of infection. For some units, including oncology, neonatology, intensive care and transplant units special ventilation may be desirable. Four degrees of risk may be considered; low risk areas as the administrative sections, moderate risk areas as the regular patient units, high risk areas including isolation unit and intensive care unit and very high risk areas considering the operating rooms (Tang et al., 2006).
f. Construction material:
The choice of construction material especially those considered in the covering of internal surfaces is very important. Floor coverings must be easy to clean and resistant to disinfection procedures. This also applies to all items in the patient environment (Lateef, 2009).
g. Water supply:
The physical, chemical and bacteriological characteristics of water used in healthcare institutions must meet local regulations. The institution is responsible for the quality of water once it enters the building. For specific uses, water taken from a public network must often be treated for medical use (physical or chemical treatment) (Walkera et al., 2007).
2. Standard precautions for protection of healthcare workers:
These measures must be applied during every patient care and during exposure to any potentially infected material or body fluids as blood and others. These include the following: hand washing and antisepsis (hand hygiene), use of personal protective equipment, appropriate handling of contaminated equipment and prevention of needle stick injuries (Talaat et al., 2003).
1. Hand washing:
Frequent and adequate hand washing is the best way to prevent spread of most nosocomial infections. The extreme importance of hand washing has been known since at least 1847, when Dr Ignaz Semmelweis discovered that washing hands before performing obstetric exams on pregnant women reduced childbirth-related infectious mortality from more than 10% to less than 1% (Jumaa, 2005).
For hand washing the following must be available running water, large washbasins which require little maintenance, with antisplash devices and hands-free controls, products as soap or antiseptic depending on the procedure facilities and disposable towels if possible for hand drying without contamination. For hand disinfection, specific hand disinfectants as alcohol rubs with antiseptic and emollient gels should be present (Naikoba and Hayward, 2001).
Wash of hands must be done after handling any blood, body fluids, secretions, excretions and contaminated items; between contact with different patients; between tasks and procedures on the same patient to prevent cross contamination between different body sites and immediately after removing gloves. Procedures will vary with the patient risk assessment. There are three types of hand wash as shown in the following table (2) (Jumaa, 2005).
1. Gloves:
Gloves protect the hands from contacting blood, droplets, body fluids and pathogen-contaminated objects so infection can be prevented when touching the eyes, mouth or nose afterwards. Gloves can also protect open wounds from contamination by pathogen. It is not certain what type of glove provides the best protection for infection control. Some studies have suggested that latex gloves are some what better in preventing penetration of water and virus than vinyl gloves (Wittmann et al., 2010).
2. Masks:
Using the appropriate respiratory protective equipment is important for an adequate protection from biological hazards. Surgical mask is the most common respiratory protective equipment. It should be worn in circumstances where there are likely to be splashes of blood, body fluids, secretions and excretions or when the patient has a communicable disease that is spread via the droplet route (Farrington, 2007).
N95 or higher level respirators filter out particulates and liquid droplets in small particle size, therefore providing protection from inhaling aerosols and micro-organisms that are airborne. N95 masks are used in high-risk wards (Grinshpun et al., 2009).
The mask must fit over the face with the coloured side of the mask faces outwards and the metallic strip upper most, while the strings or elastic bands are positioned properly to keep the mask firmly in place. When the mask is damaged or soiled, it is replaced. (MacIntyre et al., 2009).
If required to wear N-95 mask, the face-piece must be of proper fit. Compare the size of different brands to find a suitable one. To reuse a N95 mask, it should be kept in a paper bag properly before using it again. If the N95 mask is soiled or damaged, it must be replaced immediately. N95 mask should never be shared with any body or brought outside the hospital. N95 masks should not be used by persons suffering from respiratory diseases, such as asthma and emphysema having difficulty in breathing or feeling dizzy after wearing it at this time N95 masks with exhale valve can be used as it lets the hot air out, making the mask more comfortable (Cowling et al., 2009).
3. Protective clothing:
Protective clothing includes protective coverall (with attached hood) and gown should be water proof or impervious to liquids to protect the body from contamination by blood, droplets or other body fluids, thus reducing the chance of spreading of pathogen and cross-infection. Protective clothing is disposable in most cases though some can be reused after sterilization. Standard protective clothing should fit the wearer, checked before use and replaced if damaged. (Northington et al., 2007).
c. Goggles/Face shields:
Safety goggles/glasses and face shields can protect the eyes from contacting pathogen-carrying blood, droplets or other body fluids which may then enter the body through the mucosa. Goggles fit the face snugly and therefore are better than glasses in eye protection. If necessary, face shield should be used to protect the whole face (Davis et al., 2007).
d. Boots/shoe covers:
Boots/shoe covers are used to protect the wearer from splashes of blood, body fluids, secretions and excretions. Waterproof boots should be worn for heavily contaminated, wet flooring and floor cleaning. Shoe covers should be disposable and waterproof (Northington et al., 2007).
e. Caps:
Caps that completely cover the hair are used when splashes of blood and body fluids are expected. They should protect the hair from aerosols that may otherwise lodge on the hair and be transferred to other parts of the healthcare worker such as face or clothing by the hands or onto inanimate objects. Caps should be disposable, waterproof and of an appropriate size which completely covers the hair (Parmeggiani et al., 2010).
3. Sharp precautions:
Needle stick and sharp injuries carry the risk of bloodborne infection e.g AIDS, HCV, HBV and others. Essential elements of the prevention and control of diseases caused by sharp injuries infections include training and education about nature of bloodborne pathogens, activities that place HCW at risk and means to prevent disease transmission as personal protective procedures. Protective procedures are multifaceted and staged. Procedures include the wearing of puncture resistant gloves by all personnel in situations when blood and/or body fluids are present (Daha et al., 2009).
Needles must not be recapped after injections. Sharps should be collected at source of use in puncture-proof containers (usually made of metal or high-density plastic) with fitted covers. To discourage abuse, containers should be tamper-proof (difficult to open or break). Where plastic or metal containers are unavailable or too costly, containers made of dense cardboard are recommended. Needle incinerators can be another safe way of disposal. Reusable sharps must be handled with care avoiding direct handling during processing (Clarke et al., 2002).
CDC recommendations for post exposure to bloodborne pathogens (Parmeggiani et al., 2010):
• Wounds and skin sites that have been in contact with blood or body fluids should be washed with soap and water; mucous membranes should be flushed with water.
• The person whose blood or body fluid is the source of an occupational exposure should be evaluated for HBV, HCV and HIV infection.
• Post-exposure treatment should begin within 24 hours and not later than 7 days.
• Recommendations for HBV post-exposure management include initiation of the hepatitis B vaccine series to any susceptible, unvaccinated person who sustains an occupational blood or body fluid exposure. Post-exposure prophylaxis (PEP) with hepatitis B immune globulin (HBIG) and/or hepatitis B vaccine series should be considered for occupational exposures after evaluation of the hepatitis B surface antigen status of the source and the vaccination and vaccine-response status of the exposed person.
• There is no post-exposure treatment that will prevent HCV infection. For the person exposed to an HCV-positive source perform baseline testing for anti-HCV and ALT activity; and perform follow-up testing (e.g., at 4–6 months) for anti-HCV and ALT activity (if earlier diagnosis of HCV infection is desired, testing for HCV RNA may be performed at 4–6 weeks). Immune globulin and antiviral agents (e.g., interferon with or without ribavirin) are not recommended for PEP of hepatitis
• Recommendations for HIV PEP include a basic 4-week regimen of two drugs (zidovudine and lamivudine, lamivudine and stavudine or didanosine and stavudine) for most HIV exposures and an expanded regimen that includes the addition of a third drug for HIV exposures that pose an increased risk for transmission.
4. Handling of contaminated materials:
HCWs are exposed to contaminated equipment and working surfaces, protective coverings, reusable containers and glassware. All those should be cleaned and decontaminated after contact with blood or other potentially infectious materials with barrier precautions. Linens in a hospital can be a major potential source of infection since they are likely to be contaminated by patients in hospital beds. When linens are changed, they handled with barrier precautions and gathered in enclosed coded bags as soon as they are stripped from the bed and sent to the laundry (de Castro et al., 2009)..
On handling spots of blood or other spills, gloves and eye protection should be worn. Contamination should be wiped up with paper towels soaked in freshly prepared hypochlorite solution (milton or chlorine releasing tablets) containing 10,000 ppm (1%) available chlorine. If broken glass is present, first treat the spillage with hypochlorite and then carefully remove the pieces of glass with disposable forceps or scoop to a sharps bin, before wiping up. Towels and gloves should be disposed of in a yellow clinical waste bag for incineration (or an autoclave bag if in a laboratory). Hands must be washed following clearing up. Spilt blood should not be allowed to dry as potential aerosol production is greater from dried blood (CDC, 2004).
3. Transmission route based precautions:
a. Contact Precautions
In addition to standard precautions, contact precautions are indicated for patients known or suspected to have serious illnesses easily transmitted by direct patient contact or by contact with items in the patient’s environment. In addition to standard precautions, contact precautions include putting on PPE (such as gowns) prior to entry into a patient room and taking off PPE prior to exit. Patient care equipment must be dedicated with limitation of patient movement. Those patients must be placed in a private room or with patients who have active infection with the same micro-organism with no other infection (Curtis, 2008).
b. Droplet Precautions
Droplet precautions are indicated for patients known or suspected to have serious illnesses transmitted by large particle droplets, such as seasonal influenza, invasive haemophilus influenzae type b disease and invasive neisseria meningitidis. In addition to standard precautions, droplet precautions include the use of a surgical mask when working within 3 feet of the patient and the placement of the patient in a private room or with patients who have an active infection with the same micro-organism but with no other infection (Farrington, 2007).
c. Airborne Precautions
Airborne Precautions are designed to reduce the risk of airborne transmission of infectious agents as H5N1 avian influenza, SARS, measles, varicella and tuberculosis. In addition to standard precautions, airborne precautions include placement of the patient in a negative pressure room (airborne infection isolation room), if available. If a negative pressure room is not available or cannot be created with mechanical manipulation of the air, place patient in a single room. Doors to any room or area housing patients must be kept closed when not being used for entry or egress. When possible, isolation rooms should have their own hand washing sink, toilet and bath facilities (Tormo et al., 2002).
The number of persons entering the isolation room should be limited to the minimum number necessary for patient care and support. CDC recommends the use of a particulate respirator that is at least as protective as NIOSH certified N95. For patients for whom influenza is suspected or diagnosed, surveillance, vaccination, antiviral agents and use of private rooms as much as feasible is recommended. In contrast to tuberculosis, measles and varicella, the pattern of disease spread for seasonal influenza does not suggest transmission across long distances (e.g., through ventilation systems); therefore, negative pressure rooms are not needed for patients with seasonal influenza (Lateef, 2009).
4- Environmental cleaning:
Cleaning is the removal of all visible and invisible organic material (e.g., soil) from objects to prevent micro-organisms from thriving, multiplying and spreading. 90% of micro-organisms are present within “visible dirt” and the purpose of routine cleaning is to eliminate this dirt. Neither soap nor detergents have antimicrobial activity and the cleaning process depends essentially on mechanical action (Nchez-Paya et al., 2009).
There must be policies specifying the frequency of cleaning and cleaning agents used for walls, floors, windows, beds, curtains, screens, fixtures, furniture, toilets and all reused medical devices. Methods must be appropriate for the likelihood of contamination and necessary level of asepsis.
5. Disinfection of patient equipment
Disinfection removes micro-organisms without complete sterilization to prevent transmission of organisms between patients. Disinfectants must be easy to use, non-volatile and not harmful to equipment, staff or patients, free from unpleasant smells and effective within a relatively short time. Different products or processes achieve different levels of disinfection. These are classified as high, intermediate or low level disinfection. Table (8) provides characteristics of the three levels (Hedin et al., 2010).
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