Unit 3. Infection control (IC) basics and the WHO set of measures for TB IC TB Infection Control Training for Managers at National and Subnational
Unit 3. Infection control (IC) basics and the WHO
set of measures for TB IC
TB Infection Control Training for Managers
at National and Subnational Level
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Objectives
After this unit, the participant will
• understand the mechanisms of TB transmission
• be able to describe the factors affecting the risk of TB transmission (patient, recipient, bacterial and institutional factors)
• be able to list the WHO set of measures for TB infection control
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Standard precautions
• Use with every patient, at every health care visit
• Main elements include:– Hand hygiene – Respiratory hygiene, cough etiquette– Use of personal protective equipment to
avoid direct contact with patient’s blood, body fluids, secretions, and non intact skin
– Prevention of needle stick/sharp injury– Cleaning and disinfection of the environment
and equipment
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Additional precautions
Added to standard precautions depending on transmission mode of the patient’s suspected pathogen:
• Airborne (measles, chickenpox)
• Droplet (SARS, avian influenza)
• Contact (staphylococcus aureus)
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Airborne vs. droplet transmissionAirborne• Small droplet nuclei <5 microns diameter• Stay suspended in air• When inhaled, can reach the alveoli and cause
infection
Droplet • Large droplets > 5 microns in diameter. • Do not remain suspended in the air, so no
special air handling or ventilation is required• If inhaled, do not reach alveoli
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Fate of droplet nuclei vs. droplets
Droplet nuclei (airborne transmission)
• A 1.0 μm droplet nucleus will settle at a rate of 0.0035 cm/sec (or 3 m in 24 hours)
Large droplets (droplet transmission)
• Fall to ground or other horizontal surface relatively fast
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A sneeze
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Number and size of organisms
Number of organisms releasedTalking 0-200
Coughing 0-3,500
Sneezing 4,500- 1,000,000
Size of the droplets (function of air velocity)Sneeze ~3-10 m/s
75% are ~10 μm in diameter
< 25% are droplet nuclei (1-5 μm in diameter).
Wells 1955, Duguid 1945, Wells/Riley 1961, et al.
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Airborne precautions
• Place patient in airborne precaution room which has: – 12 or more air changes per hour– Control of airflow direction
• Limit the movement of the patient– Ensure patients wear a surgical mask if
outside their rooms
• Use a particulate respirator whenever entering and providing care
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What is the risk for TB transmission?
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Who can infect whom?
Patient to Worker to Visitor to
Patient
Worker
Visitor
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Factors affecting the risk of transmission
• Patient
• Recipient
• Bacterial
• Institutional
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Patient factors• Infectiousness: sputum smear, cavitation, force
and frequency of cough* • Cough-inducing procedures• Treatment (time since start of correct treatment
and adherence)*• Understanding of TB, cough etiquette*, and
adherence to IC practices• General health status (immune status,*
nutrition, co-morbidities, e.g. diabetes)
*Influence the number of infectious bacilli released
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When is TB most infectious
• When it occurs in the lungs or larynx• Until the person has
– Completed at least 2 weeks of appropriate therapy, preferably with direct observation
– Has become smear negative– Has improvement in symptoms
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Recipient factors
• Closeness, duration and frequency of contact*• Risk of TB infection (prior treatment, age,
homelessness, contact of known case, etc.)• Adherence to IC practices*• Susceptibility either intrinsic or acquired (i.e.
immune status, general health, other diseases, nutrition, age)
*Influence dose of inhaled bacilli
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Recipient factors
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Bacterial factors
• Intrinsic virulence of MDR-TB bacilli may not be greater than drug susceptible bacilli
• However, patients with MDR-TB may infect more people due to their prolonged period of infectiousness
• Previously treated cases (treatment failure, default, relapse) have increased levels of MDR-TB
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Institutional factors (1)
• Exposure in small, enclosed spaces
• Lack of adequate ventilation
• Re-circulation of contaminated air
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Institutional factors (2)
• Fixed characteristics (type, location, structure)• Variable characteristics (temperature, humidity,
rain)• Type and number of people served by institution
(crowding)• Resources available• Policies and practices governing patient
movement and housing• Time lag between detection of disease or drug
resistance (reporting and proper treatment)
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Institutional factors
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Institutional factors (3): path of the patient
• In-patients versus out-patients
• Diagnosed TB cases vs. undetected
• Intake, triage, registration
• Waiting area
• Laboratory, radiology, pharmacy
• High risk procedures
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Areas visited by TB patients
Home/referral clinics
TB Department
TB wards
Reception
OPD
VCT
Radiology
Laboratory
Pharmacy
Other departs
General wards
Maternity ward
Un
susp
ecte
d
TB
pat
ien
ts
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Institutional factors (4)path of the specimen
• Collection location and procedures
• Registration and identification number
• Storage
• Transportation
• Lab log entry
• Processing procedures
• Smear, culture, drug susceptibility testing
• Disposal procedures
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Reorganization for optimal services (functionality)
• Maximise infection control
• Minimize risk of TB transmission
• Maximise quality of patient services
• Minimize cost (capital and recurring)
Set of measures for TB infection control, WHO, 2009
1. National and subnational levels• Managerial activities
2. Facility level• Managerial activities• Administrative controls• Environmental controls• Personal protection
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What are managerial activities?
Activities used by programme managers to support and facilitate the
• implementation
• operation
• maintenance
• evaluation
of TB infection control at the national, sub-national and facility levels
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Managerial activities—national level (1)
• Identify and strengthen a coordinating body• Develop a comprehensive plan for IC to
include – Budget– Human resource requirements
• Ensure that health facility design, construction, renovation and use are appropriate
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Managerial activities—national level (2)
Set of measures--facility level
• Managerial activities
• Administrative controls
• Environmental controls
• Personal protective equipment
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Managerial activities at the facility level
• Identify and strengthen coordinating body, develop facility plan
• Rethink use of available spaces• Assess facility, conduct surveillance of TB
disease among health workers• Address ACSM for health workers, patients
and visitors• Monitor and evaluate set of TB IC measures• Participate in research efforts
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Administrative controls—facility level
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Environmental controls—facility level
Reduce the concentration of infectious particles in the air via:
• Ventilation– Natural, mechanical, or mixed mode– Can direct the flow of infectious air away
from health care workers and other patients
• Ultraviolet germicidal irradiation (UVGI)
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Personal protective equipment
Use particulate respirators
• Along with administrative and environmental controls
• In situations where there is an increased risk of TB transmission
• With comprehensive training program
• With fit testing
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Controls work at different points of the chain of transmission
Patient coughs droplet nuclei into air (administrative controls)
Droplet nuclei are suspended in the air
(environmental controls)
Exposed person breathes in M. tuberculosis
(particulate respirators)
Priority measures for IC
Control Why?
1 Administrative Prevent the generation of droplet nuclei. First line defence.
2 Environmental 2nd line defence, since cannot eliminate all TB exposure.
3 Particulate respirators
Use only with the other 2 controls, in situations with a high risk of TB transmission. Protect only the health care worker, not other patients or visitors
Managerial IC activities are required for all facilities35
Summary• TB is spread through droplet nuclei that
stay airborne for prolonged periods, and can be inhaled
• Patient, recipient, bacterial and institutional factors influence the risk of TB transmission
• WHO recommends a set of TB infection control measures including managerial, administrative, environmental, and personal protective equipment
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