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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