communicable disease control public health, year 4, mms yr 4 ph paediatrics 1

Communicable Disease Control

Public Health, Year 4, MMS

Yr 4 PH Paediatrics 1

Why do Outbreaks occur?Why do Outbreaks occur?• Groups of 3Groups of 3• 5 minutes5 minutes• Rapid feedbackRapid feedback

2 PUBLIC HEALTH PEP

How do outbreaks occur?How do outbreaks occur?

•Need to have epidemiological Need to have epidemiological disease-cause triad of:disease-cause triad of:

–agentagent–host host –environmentenvironment

•And a chain of transmission that And a chain of transmission that links the abovelinks the above

PUBLIC HEALTH PEP 3

Status: Susceptible/ Immune/ InfectedResponse: No illness/ Typical illness/ Atypical or v severe illness (e.g. immunocompromised)

Infectivity Pathogenicity

Virulence

conditions or influences not part of agent or host, which influence their interaction

HostAgent

Environment

The host-agent-environment triad

PUBLIC HEALTH PEP 4

CHAIN OF TRANSMISSION

AgeGenetic determinants

Nutritional statusUnderlying medical condition

ImmunosuppressionCo-infection

Treatment with antimicrobialsBehaviour

Psychogenic factors

Ability to survive in environment

Mode of transmissionAbility to attach, invade,

multiply in hostDuration of infectivity

Evasion of host immunityResistance to

antimicrobial therapy

Immunity of immediate contactsIncidence of infection in contacts

Human population density,movement & mixing

Vector/ reservoir densityDisease incidence in

vector/reservoirResistance to interventions in

vector/reservoirClimate & environmental change

Antibiotics in the environmentOther pathogens

Water supplySanitation

Host Agent

Environment

from Cohen J, Powderly. Infectious Diseases, Second edition. Edinburgh: Mosby; 2004

The host-agent-environment triad

PUBLIC HEALTH PEP 5

6 PUBLIC HEALTH PEP

PATHWAY

SOURCERECEPTORS

Key termsKey terms

•Index case•first case to come to the attention of the investigator: not always the primary case•Primary case •case that introduces the disease into the family/group/population•Secondary case •catches infection from primary case•Incubation period •time between between infection and developing first symptoms

PUBLIC HEALTH PEP 7

Key terms 2Key terms 2

•Latent period= time between infection and becoming infectious•Incubation period= the time interval between acquisition of infection and onset of illness/symptoms•Attack rate= proportion of exposed population that becomes clinically ill

PUBLIC HEALTH PEP 8

SURVEILLANCESURVEILLANCE


What is disease surveillance? What is disease surveillance?

systematic process of:–Collecting and collating data–Analysing data– Interpreting the results – feeding back the information to

those who need to take action

“INFORMATION FOR ACTION” 10 PUBLIC HEALTH PEP

It’s not new.....It’s not new.....•1660’s-1830’s: Bills of Mortality weekly statistics for numbers buried in each parish who died of the plague & other causes•C19th: Medical Officer of Health Reports

Since late C19th : statutory notification of infectious diseases

PUBLIC HEALTH PEP 11

Surveillance – a classical Surveillance – a classical modelmodel


Event

Real world – Expect changes

Intervention

Data

Analysis and interpretation

Information

Health care system Public Health Authority

Reporting

Decision (feedback)

Surveillance vs. Research Surveillance vs. Research SurveillanceSurveillance•Applies existing knowledge to guide the health Applies existing knowledge to guide the health system in the use of known control measuressystem in the use of known control measures - directly relevant to - directly relevant to monitoringmonitoring and and controlcontrol measuresmeasures

ResearchResearch•Pursues new knowledge from which better control Pursues new knowledge from which better control measures will resultsmeasures will results- systematic investigation, testing and evaluation - systematic investigation, testing and evaluation designed to develop or contribute to knowledgedesigned to develop or contribute to knowledge

13 PUBLIC HEALTH PEP

Creating a Surveillance Creating a Surveillance systemsystem

• TASK: What do you do when you TASK: What do you do when you are ill?are ill?


Sources of dataSources of data


Community

CliniciansClinicians


Health Protection Regulations Health Protection Regulations 20102010

• Requires :• Registered medical practitioners to notify the proper

officer of the local authority if a patient:• has a notifiable disease• has an infection that could present significant harm• is contaminated• has died with a disease or infection that could present

significant harm• Diagnostic laboratories to notify PHE when evidence of

infections caused by specified agents

http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/HealthProtectionRegulations/PUBLIC HEALTH PEP 17

DISEASES NOTIFIABLE UNDER THE PUBLIC HEALTH (INFECTIOUS DISEASES) REGULATIONS 2010

Acute encephalitis Acute infectious hepatitis Acute meningitis Acute poliomyelitis Anthrax Botulism Brucellosis Cholera Diphtheria Enteric fever (typhoid or paratyphoid fever) Food poisoning Haemolytic uraemic syndrome (HUS) Infectious bloody diarrhoea Invasive group A streptococcal disease Legionnaires’ Disease Leprosy

Malaria Measles Meningococcal septicaemia Mumps Plague Rabies Rubella SARS Scarlet fever Smallpox Tetanus Tuberculosis Typhus Viral haemorrhagic fever (VHF) Whooping cough Yellow fever


LaboratoryLaboratory


Patterns of reporting to national surveillance for Campylobacter, Salmonella, norovirus and rotavirus, UK 2008–9.

Tam C C et al. Gut doi:10.1136/gut.2011.238386

Copyright © BMJ Publishing Group Ltd & British Society of Gastroenterology. All rights reserved.


Evaluating surveillance systemsEvaluating surveillance systems

Simplicity Is system easy to access & use from perspective of various users

Flexibility How readily can it be adapted

Data quality Is data of sufficient quality & consistency to assure reliable use for intended purpose

Acceptability Are procedures for obtaining data nonintrusive, are the data useful, perceived as wise investment

Sensitivity Probability that a case will be identified

What percentage of epidemics or outbreaks are detected

Predictive value Probability of the disease/event given the surveillance data

Likelihood that alerts represent events that we are seeking to detect

Representativeness To what extent is the pattern representative of the health of the population

Timeliness Does system provide data that allows timely investigations & effective intervention

Stability Is there assurance that trends reflect health/illness & not changes in how data collected/managed


Why is surveillance important??

1. Enables timely public health action for sporadic cases e.g. contact tracing

2. Detection of outbreaks/clusters3. Monitor trends in disease4. Estimating magnitude of problem5. Can monitor and evaluate prevention and

control programmes6. Feeds into policy decisions and planning


Success looks dull….Success looks dull….

24 MMHSC Study Day

OUTBREAK OUTBREAK INVESTIGATIONINVESTIGATION

Recognising OutbreaksRecognising Outbreaks


Measles in a local authority area

What is an outbreak?What is an outbreak?An outbreak or an epidemic exists when there are more cases of a particular disease than expected in a given area, or among a specific group of people over a particular period of time

OrOne case of serious/rare disease e.g. Ebola/plague/smallpox


Why investigate outbreaks?

•To control it•To understand what happened•To prevent future outbreaks•Research and training opportunities•Programme evaluation•Public, political or legal concerns


Steps of an outbreak Steps of an outbreak investigationinvestigation

1. Verify diagnosis 2. Confirm the outbreak3. Define a case4. Conduct case finding5. Descriptive epidemiology 6. Formulate and test hypotheses7. Analytical epidemiology8. Microbiological and environmental investigation9. Implement and evaluate control measures10.Communicate findings

These steps may occur simultaneously or be repeated as new information is received


INFECTION CONTROLINFECTION CONTROL


HCAI•Mandatory Surveillance

– Meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia

– Meticillin-sensitive Staphylococcus aureus (MSSA) bacteraemia

– Escherichia coli (E. coli) bacteraemia

– Clostridium difficile infection (CDI)

•Emerging issues– CPE– VRE

31 MMHSC Study Day

Infection Control HierarchyInfection Control Hierarchy

32 MMHSC Study Day

Your 5 moments for hand hygiene

Hand Hygiene- its not difficult Hand Hygiene- its not difficult in the UK!in the UK!


• And so to group workAnd so to group work


communicable disease control public health, year 4, mms yr 4 ph paediatrics 1

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