controlling infectious disease Flashcards
(16 cards)
reproduction rate - R0:
R0 is the – number of — of an — caused by — case
Depends on — of disease, proportion — , outbreak —
R0 — : each case spreads the infection to more than one person => chain reaction → —
R0 — : on average, each case is not replacing itself in the population => — / — dies out
average
new cases
infection
one
transmissibility
proportion susceptible
outbreak response
>1
epidemic
<1
infection/outbreak
example of R0:
Without the application of any intervention
Ebola 1.5-2.5
Influenza (1918) 3
Smallpox 5-7
Polio 5-7
Measles 12-18
SARS CoV2 3.6 – 6.1 before vaccines
types of cases:
1- Index – the first case — by a clinician or health authority
2- Primary (1) – the case that — infection into a population
can only apply to — diseases that are spread from — may not be the — case (first case identified)
can have —
3- Secondary (2) – infected by a — case
4- Tertiary (3) – infected by a — case
identified
introduces
infectious
human to human
index
co primaries
primary case
2ndary case
Which of the following infection timeline pattern results in “Asymptomatic” spread?
A) Incubation period = latent period
B) Incubation period > latent period
C) Incubation period < latent period
b
- Incubation period: Time from exposure to the onset of symptoms
Latent period: Time from exposure to the point when a person becomes infectious
-The person becomes infectious before showing symptoms
This allows asymptomatic (or pre-symptomatic) transmission — they can spread the infection without knowing they are sick
how are infections transmitted - the infectious disease model :
factors influencing disease transmission
1- — :
Infectivity
Mode of transmission
Pathogenicity
Virulence
Immunogenicity
Antigenic stability
Survivability
2- — :
Intrinsic
Behavioural
Iatrogenic
3- — :
Weather and climate
Housing and sanitation
Geography
Work environment
Food and water
Social factors – poverty, education, overcrowding
agent
host
environment
1- agent:
— : ability of an agent to cause infection in a susceptible host i.e. proportion of persons exposed to an infectious agent who become infected
—-: ability of an agent to cause disease after an infectioni.e. proportion of persons infected by an agent who then experience clinical disease
—-: ability of an agent to cause severe disease
i.e. proportion of persons with the disease who become severely ill or die
—-: ability of an agent to produce an immune response
—-: genetic mutability (changeability) of an agent e.g. measles = antigenically stable (vaccination gives life long antibody protection) cf. influenza = unstable (changes each season)
—- : ability of an agent to survive in the environment
—- : amount of an agent required to cause infection in a susceptible host
—- : the habitat in which an agent normally lives, grows and multiples (can include humans, animals or the environment)
— : person, animal, object or substance from which an agent is transmitted to a host
infectivity
pathogenicity
virulence
immunogenicity
antigenic stability
survivability
infective dose
reservoir
source
2- environment as — quality , — , — , and — which includes population density, overcrowding, poverty, education
3- host:
A person or other living organism that is — to, or harbours, n infectious agent under natural conditions
(i.e. provides a suitable place for the agent to – and — )
these include intrinsic , behavioural , iatrogenic
water , temp, sanitation , socioeconomics
susceptible
grow and and multiply
what makes a host susceptible:
1- — :
Genes
Prior immunity
Age, sex
Health status, e.g. underlying immunosuppressive disease (HIV/AIDS, diabetes mellitus, chronic renal failure, cancer), malnutrition
2- — :
Isolation vs gregariousness
Personal habits (handwashing, personal hygiene, use of PPE)
Risk-taking behaviour (drugs, alcohol, unsafe sex,)
High risk environments, e.g. homeless shelters, prison, crowded living conditions
Limited contact with medical services
Poor adherence to medical advice/medication
3- — :
Corticosteroids, antirejection medicines, antineoplastic medicines
Surgical procedures and radiation therapy
Invasive devices/ implants
intrinsic
behavioural
iatrogenic
in covid :
1- prior immunity , age/sex . health status
2- behvarioral:
vs gregariousness
Personal habits (handwashing, personal hygiene, use of PPE) , high risk environment , Limited contact with medical services
Poor adherence to medical advice/medication
3- immunosuppressive tx
- transmission of infection:
Any mode or mechanism by which an infectious agent is spread to a — - three conditions required for infection to spread from one person to another:
1- The first person must be — with a microorganism
2- The second person must be — to infection with that microorganism
3- The — must be able to leave the body of the infected person and — and enter the body of the susceptible person
susceptible host
infected
susceptible
micro-organism
transfer
chain model of infectious disease:
Infection control aims to break the links
Break one link and reduce the likelihood of infection
More links broken, the better
— factors can influence all stages in the chain
chain :
— –> portal of —- —-> —- —> portal of —- —> —- —>
environmental
source ( agent)
exit
transmissio process
portal of entery
host
1- break the link - source:
How can we contain the source of the agent?
Eliminate — ( —/—)
— change of human source
2- break the link - transmission:
How can we stop transmission?
— control
—/—-
— restrictions
3- break the link - host:
How can we reduce host susceptibility?
—-
—- for contacts (e.g. chemoprophylaxis meningitis/TB)
—-
reservoir (human/animal)
behavioural
infection
isolation/quarantine
activity restriction
vaccination
prophylaxis
self isolation
factors in communicable disease emergence and re emergence:
1- host :
2- agent:
3- environment :
1-
Human susceptibility
Demographics
Behaviour
International travel and trade
Intent to harm
2-
Microbial adaptation (antimicrobial resistance)
3-
Climate
Changing ecosystems
Economic development
Public health infrastructure
Land use
Technology and industry
Poverty and social inequality
War and famine
Infectious disease notification:
-Part of infectious disease —
-List of notifiable diseases
http://www.hpsc.ie/notifiablediseases/listofnotifiablediseases/
National and international regulations for mandatory reporting
e.g. Ireland 1947 Health Act, Infectious Disease Regulations 1981
WHO International Health Regulations 2007
-All medical practitioners including clinical directors of laboratories must notify Medical Officer of Health (MOH), who in turn must notify Health Protection Surveillance Centre
All cases of notifiable infectious diseases recorded on —-
surviellence
national surveillance system (CIDR)
- Notifiable disease case definitions =
clinical — +/- – criteria +/- — link
-Possible or Probable or Confirmed
-Ensures — and — - disease surveillance:
Surveillance = ongoing — collection, collation, analysis and interpretation of health data timely dissemination of data effective action to — disease
= information for —
Surveillance is the — step towards prevention
description , lab , epidemiological
diagnosis and comparability
systematic
prevent
action
1st step
sources of surveillance data :
Collection Methodologies
1- Passive, general notification system, immunisation data
2- Active, e.g. population — during outbreak
3- Sentinel, e.g. Sentinel GP network for Influenza
4- — , e.g. Cough Calls to GP OOH services
5-KPIs/Benchmarking, e.g. Quarterly TB KPI
6-Point Prevalence surveys, e.g. — study
Systems & Software
CIDR – all notifiable diseases (Business Objects)
Health Atlas / links CSO
HIPE – ICD 10 Coded discharges
iPMS – hospitalisation data
COVAX
Statistical Analysis – JMP, SPSS, STATA
Teleform
screening
syndromic
HALT
reasons why infectious disease is under control:
Counts, incidence and prevalence ( common , risk groups? )
Morbidity/severity ( illness , aysmptomatic? )
Mortality rate/premature mortality ( risk group , mortality ratio )
Communicability/outbreak/epidemic potential ( can it spread , transmission )
Changing pattern ( ( emergence m risk groups )
Preventability ( vaccination , physical countermeasures)
Public health response ( investigation and control )
Public Perception of Risk ( public anxiety )
International concern ( intenational spread , IHR obligations )
Information gap ( new disease )
intentional obligations:
“to prevent, protect against, control and provide a public health response to the international spread of disease in ways that are commensurate with and restricted to public health risks, and which avoid unnecessary interference with international traffic and trade“ (Article 2)
Requirement to notify to WHO, any event that may constitute a Public Health Emergency of International Concern (PHEIC)
A PHEIC is an extraordinary event that:
Is a public health risk to other States through the international spread of disease
May potentially require a coordinated international response
Is serious and unexpected
EU formal restricted internet based system for notification of
Public health events of international concern (to other MS)
Public health measures being taken
Coordinated by ECDC on behalf of the European Commission
EWRS contact points in each Member State – Director, HPSC
European Centre for Disease Prevention and Control (ECDC)
National Competent Body for interaction with ECDC
