Principles of communicable disease surveillance and control.

Question 1

What is public health surveillance?

Answer 1

The ongoing, systemic collection, analysis and interpreation of health related data essential to planning, implementation and evaluation of public health practises.

Aka regular and organised data collection to inform action/application of public health interventions.

Question 2

What is the surveillance loop for communicable disease?

Answer 2

Initial ‘event’ (disease case) occurs in health care system then is reported to public health authorities.
They analyse and interpret the data from all reports to create meaningful information.
They distribute this information back into health care systems who take action to reduce diseases case, then continue to monitor and report new cases back to public health for analysis.

Question 3

What information is important to collect in surveillance of infective disease?

Answer 3

Disease frequency - prevalance and incidence
Disease severity - mortality and hospitalisation
Risk factors - age, sex, ethnicity
Location of cases
Trends over time
Cost to NHS and economy.

Question 4

What action is often taken as a result of public health surveillance?

Answer 4

Prevention and control disease
Evaluate control measures
Measure health needs
Plan new services
Stimulate and inform research
Formulate policy and guidance
Assess progress against targets
Improve preparedness.

Question 5

How did surveillance data prove useful in measles?

Answer 5

Measels - high contagious viral respiratory illness with severe complications, 2 doses MMR vaccine is preventative
Surveillence detect large inc in measels in west midlands in 2023, correlated with decreased childhood vaccination uptake.
Launched a child and YA vaccination campaign in England. Declared a national incident. Combined with media to warn of risk of measels and encourage vaccination.

Question 6

What is meant by comprehensive surveillance in public health?
Pros/cons

Answer 6

Where all healthcare providers report data
Used for low frequency or high severity diseases such as notifiable diseases
+ Provides representative coverage
- time and resource intensive
- lots of different reporters, more variation in data quality.

Question 7

What is meant by sentinel surveillance in public health?
What are the pros and cons?

Answer 7

Where only some providers report data.
Used for high frequency or low severity diseases such as seasonal influenza
+ cheaper
+ good data, if sites are selected to make an appropriate sample
- can miss cases of diseases, particularly if rare
- may not be representative of wider population

Question 8

What is meant by active surveillance in public health?
What are the pros and cons?

Answer 8

Public health agencies create methods to collect and formulate their own data either from population or health care providers
For example screening patients or sending out surveys to providers
+ quicker
+ more control over data
+ tends to higher quality and complete as ensure all questions you want answered are included
- time and resource intensive for public health

Question 9

What is meant by passive surveillance in public health?
What are the pros/cons?

Answer 9

Data is reported to public health officials, who then only need to interpret it.
For example health professionals reporting notifiable diseases or analysis of death certificates.
+ cheaper
+ can improve data quality over time
- less timely and tends to be incomplete
- limited control over what data is collected.

Question 10

What is meant by case based surveillance in public health?
What are the advantages and limitation?

Answer 10

Case-based targets a specific disease and collects information at the individual level.
Builds up a collection of reports of cases of disease.
For example lab-confirmed cases of rotavirus or clinically diagnosed conditions.
+ easier to interpret
+ fewer false positives
- less timely
- same cases wont get diagnosed/tested hence will be missed

Question 11

What is syndromic surveillance in public health?
What are the pros and cons?

Answer 11

Reports collections of symptoms (syndromes) rather than a physician or lab confirmed diagnosis.
For example number of A&E attendenaces with gastroenteritis, 111 calls for fever or google searches for cough
+ acts as early warning
+ efficient use of existing data
- less specific
- difficult to interpret
- insufficient to prompt action?

Question 12

What is voluntary reporting of public health data?
What are the advantages and disadvantages?

Answer 12

Where the system to report data exists but is not legally required
For example norovirus outbreaks in hospital
+ gives a basic understanding of what is going on
- may be unrepresentative or of low quality

Question 13

What is statutory reporting of data in public health?
What are the advantages and disadvantages?

Answer 13

Legal obligation to report certain data
For example: contacting public health authority to report notifiable diseases
+ provides more complete data sets
+ more representative data
+ easier to interpret trends
- time consuming to set up
- unsure how to enforce
- impacts of confidentiality of patients (particularly for STIs).

Question 14

What type of diseases must be reported to public health?

Answer 14

Under Health Protection Regulation 2010
- any patient diagnosed or suspected to have a notifiable disease listed.
- an infection that could or does present a significant threat to human health
- contaminated in a manner that could cause harm to human health for example food poisoning, radiation
- person who has died with (not always from) any of the above.
- causative agents identified in labs on the list below.

Question 15

Give some examples of notifiable diseases?

Answer 15

Acute infective hepatitis
Acute meningitis
Botulism
Cholera
Covid-19
Food poisoning
Invasive Group A strep
MMR
Rabies
Scarlet fever
Tuberculosis
Whooping cough.

Question 16

Who should clinicians report notifiable diseases to?
What do they then do?

Answer 16

Report to UK health security agency
Have a network of Health Protection Teams which will then investigate source and aim to control source of outbreak.
Provide advice and guidance e.g testing, prophylaxis related to the communicable disease
Conduct disease surveillance

Question 17

What is a routine notifiable disease?

Answer 17

Acute encephalitis
Scarlet fever
Lepropsy
Mumps
Rubella
Typhus

Question 17

How do I report a notifiable disease?

Answer 17

Diseases classified as urgent should be reported by telephone ASAP
Non urgent can be reported via email within 3 days.
Phone number and email address is widely available on wards and online.

Question 18

What is the middle classification of notifiable disease?
Often routine unless UK acquired or part of outbreak

Answer 18

Acute meningitis - if bacterial
Food poisoning
Malaria (UK)
Tetanus (if from drug injection)
TB - HCW or MDR

Question 19

What are some urgent notifiable diseases?

Answer 19

Measels
Meningococcal septicaemia
SARS
Small pox.
Anthrax

Question 20

Gives some examples of different sources of surveillance data.

Answer 20

111 calls
Prison reporting
Ambulance call outs
Surveys
Care homes
Lab reports
A&E attendances
Vaccination uptake
Schools
Death registrations
Whole genome sequencing
Local authorities
Hospital admissions

Question 21

What is meant by the surviellance pyramid?

Answer 21

The amount of cases that are reported to surveillance will be lower than that exposed to and developed infection
From bottom to top:
Exposed to infection
Develops infection
Develops symptoms
Seeks medical attention
Specimen is collected
Specimen tests positive
Reported to surveillance

Question 22

How can clinicians improve how representative surveillance data is of the actual health problem?

Answer 22

Prompt recognition and diagnosis of disease
Collection of appropriate specimens for testing
Prompt reporting to HPT.

Question 23

What are the different stages in the chain of infection?
How does this relate to communicable disease control?

Answer 23

Public health will try to break the chain of infection at as many of these stages as possible
Causative agent: pathogenic organism
Reservoir
Means of exit
Mode of transmission
Means of entry
Susceptible host.

Question 24

What is an incubation period of a disease?

Answer 24

The interval between initial contact with infectious agent to onset of first symptoms

Question 25

What is a latent period of a disease?

Answer 25

The interval from initial contact with infectious agent to beginning of infectiousness

Question 26

What is the infectious period of a disease?

Answer 26

Interval during which the disease may be transmitted to others.

Question 27

What is the infectious and incubation period of influenza?

Answer 27

Incubates for 1-4 days
Infectious 1 day before to 5-7days after symptoms

Question 28

What is the infectious and incubation period of hepatitis A?

Answer 28

Incubates for 15-50 days
Infectious 2 weeks before symptoms start to 1 week after jaundice onset

Question 29

What is teh infectios and incubation period of measels?

Answer 29

Infectios 4 days before to 4 days after rash onset
Incubates for 7-21 days

Question 30

What is the infectious and incubation period for menigococcal disease?

Answer 30

Incubates for 3-5 days
Infectious from 7 days before onset until 24 hours of appropriate antibiotics

Question 31

What is the infectious and incubation period of norovirus?

Answer 31

Incubates for 12-48 hours
Infectious until 48 hours after symptoms end.

Question 32

What are the two different timelines of disease progression and the time periods that they contain?

Answer 32

Split into timeline A = Latent to infectious
Timeline B = incubation to symptomatic

Question 33

What is the subclinical phase of an infection?

Answer 33

When the person is infectious but asymptomatic
This is the time between the end of the latent phase and the end of the incubation period/start of symptomatic period

Question 34

What are the disease implications when the latent period is shorter than the incubation period?

Answer 34

Large subclinical phase
This is when the patient is infectious but asymptomatic
Hence will not seek treatment, will not know ill, will not isolate, more likely to socialise with vulnerable groups or large population and spread the infections unawares to others.

Question 35

What are the two methods of measuring disease transmissibility?

Answer 35

Basic reproduction number R0
Effective reporduction number R

Question 36

What is basic reproduction number as a method of measuring disease transmissibility?

Answer 36

R0
The average number of new infections a single case of a disease will cause in a completely susceptible population
Usually estimated using mathematical models
R0 value are not constant over time and place - population density, climate, social organisation etc

Question 37

What is effective reproduction number as a method of measuring disease transmissibility?

Answer 37

R
Average number of new infections a single case of disease will cause taking account any immunity within the population
R = 1 = sustained transmission
R<1 gradual decrease in transmission (curve shape)
R>1 gradual increase in transmission (curve shape)

Question 38

What is meant by a disease outbreak?

Answer 38

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.

Question 39

What is an outbreak control team?

Answer 39

A multi-agency group established to coordinate the investigation and control of an outbreak.
May include UK health protection agency, DIPC, microbiologist, media manager etc.

Question 40

What is the role of an outbreak control team?

Answer 40

Detect outbreak - review surveillance information
Investigate - find cases, arrange lab testing for possible cases, investigate sources of illness, epidemiological study if needed
Control - advise on treatment, contact tracing, chemoprophylaxis, decontamination, vaccination etc etc
Prevent - produce final outbreak report with lessons for future, training sessions, research into disease spread.

Question 41

Who are the key members who usually attend an Outbreak Control Team meeting?

Answer 41

UKHSA consultant in Health Protection
UKHSA Protection Practitioner
UKHSA consultant epidemiologist
UKHSA consultant in Public health infection
UKHSA communication manager
UKHSA administrative support
Representative from public health laboratory.

Question 42

Who may also attend an outbreak control team meeting when needed?

Answer 42

Trust IPC team
NHS integrated care board
Local authority environmental health officer
UKHSA Food, water and environmental lab

Question 43

What is the role of whole genome sequencing in monitoring TB?

Answer 43

Lab procedure to determine all specific nucleotide sequence of most or all an organisms genome
Quantifies relatedness to other samples by looking at genetic code - confirm organism, indicate different strains, indicate same cause, indicate mutations no longer protected under vaccines.
Results from different tests can be plotted on a blobogram.

Question 44

What is the typicall whole genome sequencing process for a TB case?

Answer 44

Patient with TB presents to healthcare
Sample collected for culture at local lab
Culture isolate sent to reference lab
Lab conducts whole genome sequencing
Results shared to inform action.

Question 45

What are the benefits of whole genome sequencing a TB infection?

Answer 45

Distinguish reinfection from reactivation (change in sequence v same)
Predict drug resistance patterns in order to guide appropriate treatment
Identify clusters requiring further investigation and follow up
Identify cases not part of cluster - save public health resources
Idenfity and better understand at risk groups
Monitor effectiveness of TB control policies
Meet interventional surveillance obligations.

Question 46

How does TB surveillance inform the TBA action plan for England 2021-2026?
What is this plan?

Answer 46

Data can be used to set and monitor progress against targets for service improvement
TB action plan for Englandgives national priorities to prevent and control TB.
For example: 80% of pulmonary TB cases should be confirmed by sputum samples.

Question 47

What is TB surveillance used for specifically?

Answer 47

Set and monitor progress against targets for service improvement
Identify unment needs and inform development of new services
Monitor progress towards international targets - and facilitate further investment if off track

Question 48

What is the national Latent TB Infection (NLTBI) Testing and Treatment Programme?

Answer 48

Launched in 2015
tests and treats migrants aged 16-35yrs arriving to UK from high TB incidence countries
Promopted by data showing most TB cases in migrants due to reactivation hence present on arrival.

Question 49

What is the WHO End TB strategy?

Answer 49

Sets global targets for TB control, made in 2015
90% reduction in TB incidence by 2035
95% reduction in TB deaths by 2035
England is currently not on track to meet this.