Week 2 - Control Of Communicabke Disease Control - HS Flashcards
Why is infectious disease Important?
- it’s a global burden
- UK priorities :
Health care associated infections - impact on health service delivery
Antibiotic resistance
New and emerging infections
Chain of infection
Infectious agent -> Host > portal of entry -> mode of transmission -> reservoir/environment
BInfectious agent/ pathogen has to be …
- ability to reproduce
- survival (incl environment )
- Ability to spread
- infectivity ( ability to cause infection also consider colonisation without infection )
- pathogenicity (severity of the illness
Reservoir/environment has to be …
- exposures - don’t forget relationship as a host issue
- animals as reservoirs
- other humans
- water systems
- environmental contamination
What kinds of modes of transmission are available?
1- respiratory spread
: droplet (3 feet)
: airborne(suspended particles)
: plus aerosolisation of water
2- ingestion : direct consumption : hand to mouth : contamination from people (person to person spread) : contamination from environment 3- blood borne
4- sexual contact
The different portal of entries
- mouth
- nose
- ear
- genital tract
- skin ( breakdown of barrier )
What host factors make them suspectible to infection from organisms ?
- chronic illness
- nutrition
- age (the very young and the very old )
- immunity (immune conditions ; chemotherapy; transplant etc)
- lifestyle factors ( drugs, alcohol, sex , occupation , poverty, leisure activities )
Example of an outbreak of an Infectious disease
Measles outbreak in a prison
How did measles outbreak occur
: infectious agent (IA)
- measles is highly infectious (15 mins in the same room )
:Reservoir/environment (E)
- humans only ; crowded enclosed institution , lack of isolation facilities , the dinner queue
: mode of transmission (MOT)
- droplet spread , cough , sneezes
: portal of entry (POE)
- respiratory tract
: host (H)
- young adults most UK born but some non UK born , chaotic lifestyles not sure if immunised with MMR at birth ( no health records available)
How did it get controlled ?
Mass vaccination
Difficulties faces in controlling measles outbreak
- long incubation period
- consent
- identification of new cases
- isolation of cases
- vaccination ( who pays and who does it in this setting )
Legionnaires disease outbreak in Stoke
:IA
- legionella
: E
- survives in amoebic sludge in water systems and can grow at certain temps
: MOT
- droplet or aerosois (showers, sprays, fountains, car washes , air conditioning , hot tubs etc )
: POE
- respiratory
: Host
- generally older people are vulnerable to infection with pre existing respiratory conditions
Food poisoning outbreak - E.coli in Germany
\:IA - E.Coli (usually O157) VTEC is .... - high mortality and morbidity , haemolytic Uralemic syndrome \: E - cattle guts, other animal reservoirs, soil survival \: MOT - ingestion ,person to person spread \: POE - GI tract \:H - babies and young children aged 5
Gonorrhoea outbreak in England
\:IA - gonorrhoea - high level antibiotic resistance - risk of untreatable infections \: E - humans \: MOT - sexual contact \:POE -genital tract , pharynx \:H - lifestyle risks , unprotected sex , number of patients , high risk MSN cohorts
Surveillance
Systemic collection, collation and analysis of data and dissemination of the results so that appropriate control measure can be taken
Measles outbreak
- NOIDS (notice of intent to deny)
- lab testing
- public health , follow up all contacts
Problems : rashes look very similar not everyone notifies , lab test is not routinely available, lab test takes Time to come back - issue in example of offenders not wanting to disclose illness .
Legionnaires outbreak
- lab test
- NOID
- enhanced surveillance questionnaire
- monitoring
Problems - presenting illness may be easily diagnosed as something else , test may not be done , test is not that great , need to confirm at a reference lab , clinical may not remember to notify , ESQ relies on recall ( recall bias ) , diffcult to complete.
Food poisoning outbreak
- NOIDS
- lab tests
- food complaints
- syndromic survelliance
- investigation if exceedances
- enhanced survelliance questionnaires
- outbreak specific questionnaires
Problems : mild cases don’t present, doctors don’t test. Recall bias for food eaten in the past , ingredients hard to identify , food distribution in the modern world is complex
Gonorrhoea outbreak
- GUM reporting (quarterly only at best)
- relies on GUM notifying increases
- lab tests to confirm organism and antibiotic resistance
- reference lab to confirm
- whole genome sequencing
- enhanced survelliance
Problems : late identification , chaos of life , non attendance , non disclosure of partners , partners not being tested , sexual health promotion and target audiences , behaviour change diffcult
Healthcare associated infections
- Norovirus (viral gastroenteritis ) , Burden on hospitals
- Carbapenemase producing organisms (CPO) - antibiotic resistance
- MERs -CoV - novel or emerging infections ; hospital as the point of amplification
Carbapenemase producing organisms (CPO)
Carbapenems are a powerful group of broad spectrum beta lactams antibiotics . Last effective defence against infections caused by multi resistant bacteria, such as some Strains of klebsiella pneumoniae and escherichia coli
Resistance to CPO had emerged and beginning to spread . New antibiotics needed to counter bacteria with this resistance and hospitals need good infection control to prevent their spread.
Control of HCAI
- hospital environmental hygiene ( incl isolation of cases )
- hand hygiene
- use of personal protective equipment (PPE)
- safe use and disposal of sharps and
- principles of asepsis
