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communicable disease control (Hawker 3rd edition) > Hawker 3rd edition > Flashcards

Hawker 3rd edition Flashcards

1
Q

What are the components of the epidemiological triangle

A

The agent, a susceptible host, and environmental factors

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2
Q

Example of agents

A

.Virus
.Bacteria
.Fungus
.Parasites

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3
Q

Name some examples of Host factors

A

age, sex, socioeconomic status, ethnicity, lifestyle factors, genetic makeup, etc.
All these factors influence host probability/ lvl of exposure, susceptibility and response to the agent

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4
Q

Name some example of environmental factors

A 
Geology
climate
physical surroundings
biological factors (population of insect vectors in an area)
Socioeconomic factors
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5
Q

Define endemic

A

“A persistent low or moderate level of disease”

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6
Q

Define hyper-endemic

A

” A higher persistent level of disease”

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7
Q

Define sporadic

A

“An irregular pattern with occasional cases occurring at irregular intervals”

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8
Q

Define Epidemic

A

“When the occurrence of an infection exceeds the predicted lvl for a given time period” the word outbreak is also used for this

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9
Q

Define pandemic

A

” When epidemic spreads over a wide geographic area”

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10
Q

What does an epidemic curve show?

A

a frequency histogram of number of cases against time or date of onset

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11
Q

What is a point source outbreak

A

Exposure to an infectious agent taking place over a relatively brief period.

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12
Q

What does the epidemic curve for a point source outbreak look like?

A

http://www.med.uottawa.ca/sim/data/public_health_epidemic_curves_e.htm

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13
Q

What is a propagated outbreak

A

An outbreak that spreads from person to person

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14
Q

What does the curve for a propagated outbreak look like ?

A

http://www.med.uottawa.ca/sim/data/public_health_epidemic_curves_e.htm

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15
Q

Why does an epidemic wane after a few generations

A

The number of people susceptible falls below a critical lvl

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16
Q

What is a mix epidemic?

A

An epidemic in which the epidemic curve shows both common source and propagated epidemic features due to secondary person-person spread

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17
Q

What two rates are used to describe the occurrence of infection diseases

A 
Prevalence= existing cases at a given point in time/ persons at risk
Incidence= New cases over a given time period/ persons at risk
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18
Q

What is the pathway for the chain of infection

A

Agent leaves the reservoir or host through a portal of exit and is conveyed by a more of transmission. It enters a susceptible host via a portal of entrance

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19
Q

What is a reservoir and describe some example

A

A location in which the agent normally lives and multiplies. This can be a person, animal, arthropod, plant , soil, a substance or a combination of these things. Note this can be different from source or vehicle of infection.

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20
Q

What is the source/ vehicle of infection

A

The mode of transport used by an infectious agent to pass to a host

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21
Q

What colonisation in relation to infection

A

The presence of a micro-organism in or on a host, with growth and multiplication BUT without sign of infection

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22
Q

What are zoonses

A

Infectious agents which are transmissible from animals to humans

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23
Q

What is the portal of exit

A

The path used by the infectious agent to leave the host. This tends to be an area where the agent is localised for example the respiratory tract

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24
Q

What is the portal of entry

A

The route used by the infectious agent to enter a susceptible host

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25
Q

What is the mode of transmission

A

The mechanism by which a infectious agent is spread from a source/ reservoir to a susceptible person.

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26
Q

What is the natural progress of a disease

A

The progression of a disease in an individual without intervention

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27
Q

What is the incubation period

A

A period of time in which the infectious agent is present within the host, but does not cause any pathological changes or such changes are subclinical. This period ends with the onset of disease . For any given disease the incubation period has a range and mean value

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28
Q

When does a screening program attempt to detect a disease

A

The incubation period or the early phases of its natural history

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29
Q

When are diagnoses made

A

On the onset of symptoms, where changes have moved from subclinical to clinical. In some people the disease never spreads to a clinically apparent illness. If they do manfest they can range from mild to fatal

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30
Q

What is the infectious period

A

The time point in which an infectious agent may be transmitted directly and indirectly from an infected person to another person

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31
Q

When are disease are most infectious

A

Depends on the infectious agent. Some disease are more infectious during the incubation period than the onset of illness.

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32
Q

What are the 3 categories of transmission

A

.Direct transmission- this is via direct contact such as touching , kissing ect
.Indirect transmission- can be Vehicle-borne can involve fomites, food . The agent may or may not multiple on the vehicle before transmission. The other formis vector born such as being carried by an insect. This does not require multiplication or development of the agent
.Airborne spread- dissemination if a microbial aerosol to a suitable port of entry, normally the respiratory tract

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33
Q

Name some examples of direct transmission

A

Direct route- Infection via skin, mouth, eyes spread by touching and infected area or person
Respiratory route-sneezing, coughing, from an infected person close by
Faecal to oral- when faeces are transferred directly to the mouth of the susceptible host

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34
Q

Name examples of indirect transmission

A

Faecal-oral route- Contaminated food or objects like flush handles. Indirect animal vectors such as flies may transfer the faeces.
Bloodborne route. The transfer of blood or body fluids from an infected person to another person via a break in the skin, a bite wound etc
Respiratory route- droplets from mouth and nose may contaminate hands and fomites and thus contaminate those who touch them

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35
Q

Example of diseases which are air-borne

A

Legionella, coxiella

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36
Q

What standard precautions are used to prevent disease

A

.Handwashing
.Covering of wounds or skin lesions
.Use of protective equipment eg gloves
.Respiratory and cough hygiene and etiquette
.Prevention and management of needlestick injuries, injuries from sharp and blood splash incidents
.safe disposal of contaminated waste
. Managing spillage of blood and body fluids
.Decontaminating equipment including cleaning, disinfection and sterilisation
.Safe collection and transport of specimens
.Maintaining a clean clinical enviroment
.Safe management of used linen
.Place patients with infections in appropriate accommodation

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37
Q

What is the step process when dealing with a public health issue

A 
.Define the problem
.collect the necessary information
.Undertake a risk assessment
.Identifying good practice
.implement the response
.Evaluate the outcome
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38
Q

What two questions need to be asked when dealing with a communicable disease

A

1- where did the case get it from?

2- Is the case likely to pass it on?

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39
Q

What is meningitis

A

The inflammation of the meninges .

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40
Q

What is meningism

A

Meningism is the group of signs and symptoms that accompanies the inflammation. Note you can have meningitis without meningitis but meningitis is the most common cause.

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41
Q

What are the classic symptoms of meningism

A

Headaches
neck stiffness
nausea or vomiting
photophobia

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42
Q

What is the cause of meningitis caused by

A

Acute meningitis is nearly always caused by:
1-viral or bacterial
2 fungal and protozoal infection can occur but rely on immunosuppressed patients

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43
Q

What viruses can cause meningitis

A

Commonly caused by enterovirus infection eg echovirus or coxsackievirus. Viral meningitis is common but most cases are mild or inapparent

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44
Q

Rare viruses that can cause meningitus

A 
.Poliovirus
.Mumps virus
.Influenza type A or B
.Rubella
.Epstein-barr virus
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45
Q

Bacterial meningitis is caused by

A

.E.coli- particularly emergency in infants
group B- streptococci - again common in infants

.Meningococcal meningitis- common in older infants and younger children. Caused by Neisseria meningitidis

.Haemophilus influenzae- occasionally occurs in unvaccinated children and adults. Has a slower onset than meningococcal

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46
Q

What is a common sign of meningococcal Meningitis

A

A haemorrhagic rash

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47
Q

What bacteria causes meningococcal DISEASES

A

Neisseria Meningitidis

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48
Q

What are the two Meningococcal DISEASES

A

Meningitis- inflammation of the meninges

Septicaemia- a systemic infection with widespread signs, and generalised organ damage

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49
Q

What is the reservoir for Neisseria Meningitidis

A

Humans are the only reservoir

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50
Q

Why is Neisseria Meningitidis such a problem

A

the incubation period is short and therefore kills a person quick

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51
Q

Meningococcal meningitis symptoms

A 
Headaches
neck stiffness
nausea or vomiting
photophobia
fever
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52
Q

What are the symptoms of meningococcal septicaemia

A 
Cold hands and feet
Circulatory collapse
Pale, blotchy or mottled skin
Muscle or joint pains
Petechial, non-blanching rash (doesn't disappear when pressed), becoming purpuric (purplish discolouration of the skin)
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53
Q

Why does meningococcal septicaemia cause these symptoms

A

As side effect of the immune system attacking the disease. The proteases used to break down the bacteria also can break down the capillarity lining

54
Q

What laboratory test can we use for bacterial meningitis

A

A gram stain. Due to the bacteria being gram negative, the stain will show their presence. The only exception is when TB causes meningitis

55
Q

What common investigation tests are used for bacterial meningitis

A 
Blood culture- this may show negative result if the patient has received antibiotics before admission
•Lumbar puncture-  this may show negative result if the patient has received antibiotics before admission. Clinicians are reluctant to conduct a lumbar 
•Throat swab
•Rash aspirate
•PCR for N meningitidis
•Serology
•Full blood count
•CRP (inflammatory marker)
56
Q

What are the diagnostic methods for meningitis

A

Gold standard is culture of the germ from a normally sterile site: e.g. cerebrospinal fluid, blood, joint fluid
•Culture from throat swab, rash aspirate
•Direct microscopy: Gram negative diplococci
•PCR for N meningitidis
•Antigen detection (especially for Group C)
•Serology (retrospective)

57
Q

When should you notify about a possible outbreak for meningitis?

A

Notify on suspicion – don’t wait for laboratory confirmation as public health action needed ASAP, better to be safe than sorry according to Edward

58
Q

What are the three types of cases in the development of an outbreak

A

Confirmed case: clinical diagnosis with lab confirmation (immediate PH action)
Probable case: clinical case with no lab confirmation, but meningococcal disease is most likely (immediate PH action)
Possible case: no lab confirmation and other diagnosis is equally likely (no immediate PH action)

59
Q

What is the most common type of Neisseria Meningitidis in europe and what is the common type in asia and africa

A

Europe and americas- B and C

Asia, africa- A

60
Q

What preventative and control measures can we take for hygiene for meningitis

A

General measures such as hand washing, particularly in hospitals. Enteroviral meningitis usually spreads as a result environmental contamination

61
Q

How can we reduce the chance of pregnant women passing on bacterial meningitis

A

Intrapartum antibiotic treatment for colonised women. Useful for Group B streptococcal meningitis

62
Q

What is a population approach we can take to reduce lvls of meningitis

A

Immunisation in childhood especially MMR vaccine

63
Q

what type of vaccine is given in the uk and who to (for meningitis) ?

A

Meningitis type C. It is given to those under 18 and to students starting university and those under 25

64
Q

Why is group B vaccine for meningitis not given?

A

Biologically difficult to produce.
•Antigenically similar to brain protein.
•In UK, multiple strains of serogroup B, so not easy to produce a “one size fits all” vaccine.
•Group B vaccine developed, currently given routinely for infants from 1 September 2015, but ongoing issues with uncertainty of effectiveness and high costs

65
Q

What is the purpose of Chemoprophylaxis

A

This is given to close contacts of a case, meningococcal and Hib disease. It is a type of antibiotic which is designed to clear out the throat carriage where the bacteria reside. This therefore prevents further spreading of the bacteria. It is not appropriate viral pneumococcal meningitis

66
Q

What food safety measures for meningitis

A

For listeria meningitis is preventable by avoiding high risk foods such as:
.soft cheese
pate
cook-chill foods
This is important for immunosuppressed and those pregnant

67
Q

Where are the common clusters for meningitis

A

Most common in teenagers/youths

•Outbreaks occur in schools/colleges

68
Q

What does the action plan depend on for meningitis

A

Attack rate
•Isolation of the same organism
•Establishing a link between cases
•Public anxiety

69
Q

How do you investigate cluster links in the community for meningitis

A

Look for links
•Define an at risk population
•Calculate age-specific attack rates
•No specific threshold, but look for a substantial increase

70
Q

How do you respond to a case or cluster of meningitis(more indeepth)

A

.1st priority is establishing a diagnosis by working with microbiologists and clinicians
.2nd if it is viral meningitis then no further steps are needed at this stage but it may be necessary to provide information to GP’s if the case appears to be linked
. In the event of a bacterial case; 1 further investigation is needed to determine the bacteria causing the disease
.Establish if cases are linked
.Apply chemophylaxis and vaccination program when necessary

71
Q

How do we define a GI infection

A

Any infection from whatever source, of the GI tract. Tends to result in common symptoms such as vomiting and diarrhoea.

72
Q

How many people in the uk attend their GP with acute gastroenteritis ?

A

1 in 30 but many more suffer without attending their GP

73
Q

What are the common causes of GI inefections

A

.bacteria
.viruses
.parasites
.In some cases chemicals or toxins (from things such as shellfish and fungi)

74
Q

What are the common Gi infections

A 
.Amoebic
.bacillary dysentery
.cholera
.typhoid
.paratyphoid fevers
.noravirus
.Campylobacteriosis
.E.coli
75
Q

What is Gastroenteritis

A

Acute diarrhoea and/or vomiting caused by a microorganism or toxin, directly acting on the GI tract. This results in inflammation of the bowel which produces these symptoms

76
Q

What property of diarrhoea is important to observe?

A

Consistency of stool is more important than frequency

77
Q

What is food poisoning

A

An illness which occurs after the ingestion of food. It is commonly but not always gastrointestinal

78
Q

What two pathogens are not considered causes of food poisoning despite being spread through ingestion

A

.Typhoid.
.Hepatitis A
.Brucellosis

79
Q

What does a short incubation period result in?

A

Most likely vomiting as the agent has not has much time to move down into the GI tract

80
Q

How long is the average incubation period for staphylococcus aureus

A

2-4 hrs

81
Q

How is staphylococcus aureus transmitted

A

It normally come from a food handler will have an infection. It can be spread via a wound, a boil or even asymptomatic staphylococcus in the nose or skin

82
Q

How does staphylococcus aureus cause infection

A
  • Staphylococcus lands on food after its been cooked
  • under the right condition it grows and forms a toxin
  • note only certain types of staphylococcus produce enterotoxin
  • Staphylococcus can not survive boiling or freezing but the toxin does
  • The ingested toxin causes vomiting
  • It has a short incubation period
83
Q

What foods do staphylococcus prefer

A
  • slightly sugary or salty food

- Foods which have been left at room temperature either before or after cooking

84
Q

What is the difference between Bacillus cereus (emetic type ) and Staphylococcus

A

It is naturally found in food unlike Staphylococcus, especially things such as rice

85
Q

What is the pathway for bacillus cereus to cause disease

A
  • in warm moist conditions bacillus cereus will grow and produce toxins
  • The bacillus is not destroyed completely by boiling as it develops spores
  • For example if boiled rice is let to cool slowly, the spore will become vegatated and produce toxin which will emetic
86
Q

How do you diagnose bacillus cereus poisoning

A

cannot be made solely by identifying the microorganism as it may no longer being in the food. The best method is finding the type of toxin and establishing if it is high concentration. It must be found in the food and in the vomit or stool

87
Q

How do you diagnose staphylococcal poisoning

A

cannot be made solely by identifying the microorganism as it may no longer being in the food. The best method is finding the type of toxin and establishing if it is high concentration. It must be found in the food and in the vomit or stool

88
Q

Name two causes of gastroenteritis which have a short incubation period and are not microorganisms

A
  • raw red kidney beans

- Heavy metals

89
Q

How long is bacillus cereus incubation period

A

1-6 hrs

90
Q

Describe Salmonellas

A
  • Salmonellas are an extensive species of organisms that are probably the most common cause of food poisoning
  • It can infect animals, birds and humans
  • It requires a high dose to cause symptoms
91
Q

What are the three ways salmonellas contamination can occur

A

1-method infection of poultry or animals from feed. This consumption of infected animal produce results in infection. This occurred with infected chicken eggs
2- Salmonella can spread directly to food or water through fecal contact
3- cross contamination may occurs from one food from another in the kitchen

92
Q

What is clostridium perfingens

A

is a Gram-positive, rod-shaped, anaerobic, spore-forming pathogenic bacterium of the genus Clostridium.C. perfringens is ever present in nature and can be found as a normal component of decaying vegetation, marine sediment, the intestinal tract of humans and other vertebrates, insects, and soil.

93
Q

What is the pathway for infection for clostridium perfringens

A
  • The bacterial spore get onto food contaminating them
  • In the scenario of inadequate reheating or if meat is cooked in bulk,
  • The spores of clostridium perfringens germinate during the cooling process and multiply further especially if left for a long time in warmth
  • Once ingested a toxin is formed from multiplying bacteria in the intestine
  • Causing colic and diarrhoea
94
Q

How can you diagnose clostridium perfingens

A

Finding the organism in food or stool is not enough. What is needed is finding high numbers of clostridium perfringens
enterotoxins are also available as a suitable method of diagnosis

95
Q

What is the incubation period of clostridium perfingens

A

8-24 hrs

96
Q

What is Clostridium botulinum

A

a Gram-positive, rod-shaped, anaerobic, spore-forming, motile bacterium with the ability to produce the neurotoxin botulinum

97
Q

What does Clostridium botulinum do to the body?

A

Prevents the release of acetylcholine causing muscle to be in a state of paralysis

98
Q

What three types of botulinum affect humans

A

A
B
E-found in fish

99
Q

Symptoms include?

A

Nausea, vomiting or diarrhoea followed by symmetrical paralysis of the cranial nerves leading to blurred vision and difficulty in swallowing and speaking

100
Q

What is Shignella

A

a genus of Gram-negative, facultative anaerobic, nonspore-forming, non-motile, rod-shaped bacteria , that is the cause of human shigellosis. It is one the world’s leading cause of diarrhoea

101
Q

What is shigellosis

A

A disease caused by the gram-negative bacteria shignella which leads to dysentry

102
Q

What is the pathway shignella takes to cause disease

A

It invades the distal part of the small intestine and the colon and causes acute watery, mucoid or bloody diarrhoea . Fever and intestinal colic also commonly occur

103
Q

How is diagnosis of shigellosis made

A

Isolation of the organism from stool samples and serogrouping to identify the strain

104
Q

How does shignella spread

A

Unlike simonellas, it does not survive well in food although some cases have occured from lettuce.

105
Q

What is E.coli

A

is a Gram-negative, facultatively anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms.Most E. coli strains are harmless, and some strains make up the normal flora of the gut and have a symbiotic relationship with the host.

106
Q

what are the three methods e.coli cause disease

A

.-enteropathogenic

  • enterohaemogenic
  • enteroinvasive
107
Q

what is E.coli 0157 method of transport into a human

A
  • Found naturally in a cows stomach but does not cause disease
  • When the cow is slaughtered, if the meat comes into contact with feces or stomach contents it can become infected
  • person eats uncooked meat
  • you can also get it from contaminated raw milk, contaminated water
  • essentially ingesting anything contaminated
108
Q

What are the high risk setting for E.coli 0157

A

. Nurseries
.Restaurants
.Petting farms
.ECT

109
Q

What are the particular at risk groups for E.coli 0157

A

. children under 5

.older people

110
Q

What can not be done to reduce GI infections

A

Vaccinations- many GI pathogens do not have vaccines

111
Q

What can governments do to prevent GI infections

A

Implement a stick food and safety procedures to retailers. This is an issue within developing countries

112
Q

What is HACCP

A

Hazard Analysis Critical Control Point. This is a system used in the food industry in identifying and assessing hazards in food and establishing control measures needed to maintain a cost-effective food saftey programme

113
Q

What are the measures local authority can take to prevent GI infection

A
  • Reinforce food saftey standards via health inspections
  • excluded cases/carries of infection from work/school and compensate them
  • seizure of food and closure of premises that present an imminent risk
  • Educate the public on food handling (can be nationally implemnted as well)
  • Encourage hand washing after eating or going to the toilet
  • Adequate infection control policies in school, hospitals, nursing home, ect
114
Q

What important epi data should be reported for GI infections

A

-Surveillance to detect outbreaks
-Food poisoning cases even is they are suspected
-Water born infections
-Levels of dysentery
- levels of viral hepatitis, cholera, typhoid
This is all done is the better to be safe than sorry principle

115
Q

When issues occurs with a GI infection individual cases

A

It is not usually possible to identify the organism causing gastroenteritis on clinical grounds in individual cases

116
Q

What steps should be taken when dealing with an individual gastroenteritis cases

A
  • limit secondary spread from identified cases via provisions of general hygiene advice to all and by specific exclusion from work/school/nursery of those at risk of transmitting the infection
  • Collect dataset to compare this case with other cases and identify any common exposures and potential outbreaks. ( used a standardised procedure to do this)
  • Collect faecal samples from the cases of food poisoning or dysentery. Important in identifying if a serious pathogen is involved
  • Set up a local team that includes local environmental health officers, microbiologists and clinicians
  • request GP’s report any information similar to this case
117
Q

What should be the response to gastroenteritis clusters

A
  • Discover the microbiological agent using stool samples from the most recent patients and identify all relevant organisms. The agent will determine the urgency of the investigation to prevent further exposure to a source.
  • Control measures to be introduced
  • In the time needed for clinical results to arrive, details should be collected from all reported cases in order to build a profile on symptoms, incubation period, severity and duration of illness. These can be compared to case histories for similarities
  • conduct on environmental investigation
118
Q

When conducting an environmental investigation for a GI infection

A

1- food sources, storage, food prep and cooking procedures, temperature control after cooking and reheating
2-Symptoms of gastrointestinal or skin disease or testing for faecal carriage in food handlers
3- General state of knowledge of the staff and condition of the premises
4-examination of records of key controls such as pest control and temperature
5-Whether samples of food are available for examination/analysis and whether environmental swabbing or water sampling is appropriate

119
Q

What is characteristic about influenza?

A
  • upper and lower respiratory tract infection
  • malaise ( a general feeling of uncomfort)
  • Fever
  • Aches and pains
  • occasionally a dry cough
120
Q

What are the three genera of influenza

A
  • A
  • B
  • C
121
Q

Out of the three genera, what is the scale of seriousness ?

A

Influenza A is the most serious. This causes major pandemics and is associated it pneumonia. Type B can cause severe outbreaks (compared to type C), and mainly impacts school children. Type C causes mild sporadic cases and rarely results in an outbreak

122
Q

What is the method of transmission for influenze

A
  • respiratory secretions- air droplets and small particle aerosols
  • indirect: i.e in direct contact with contaminated surfaces . This may cause a slowly evolving outbreak with a low attack rate
123
Q

What facilitates influenza transmission

A
  • overcrowding

- in closed spaces (especially with people who are susceptible)

124
Q

What is the natural reservoir for influenza

A

it is zoonotic particularly waterfowl. Transmission directly from waterfowl is rare but new strains can spread directly or through an intermediary such as a pig

125
Q

What type of influenza only infects humans

A

type B

126
Q

The two proteins Haemagglutinin(H) and Neuraminidase(N) are used to class influenza subtypes. What are they?

A

Both Haemagglutinin and Neuraminidase are surface proteins found on the surface of the virus. Haemagglutinin acts hook which binds the virus to cells while neuraminidase is an enzyme which allows new viruses to escape from the host cell.

127
Q

Why is Influenza A so difficult to deal with?

A

Has a lot of genetic mutations

128
Q

Why is seasonal flu a thing

A

Due to antigenic drift causing the virus to change a bit every year

129
Q

When does seasonal flu occur

A

Occurs most often in the winter months and usually peaks between December and March in the northern hemisphere. Flu like symptoms can appear in summer but this is most likely due to another virus. In topical conditions there is sometimes nothing like seasonal flu

130
Q

What is antigenic shift

A

Gene re-assortment & major antigenic variation, this can result in pandemics

131
Q

How do we diagnose influenza

A

Take swabs from Nasopharyngeal aspirates, nasal swabs or throat swab.
carry out immunofluorescence to allow isolation of virus, then conduct either rapid antigen testing, PCR or serology

communicable disease control (Hawker 3rd edition) (1 decks)

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