2021 Communicable Disease Flashcards
List two groups that are disproportionately affected by TB
foreign-born, Indigenous Canadians
List 5 reasons for mandatory reporting of certain diseases?
- to identify and control an outbreak
- to prevent spread if the disease presents a significant threat to individuals or a subset of the population (e.g. Lassa Fever)
- if the disease is preventable with immunization (e.g. polio, diphtheria, congenital rubella)
- if infected individuals require education, treatment, and/or partner notification (e.g. gonorrhea, TB)
- surveillance (to monitor disease trends over time)
Define primary and secondary vaccine failure.
Primary vaccine failure: Failure to respond to vaccine (no antibody level) Secondary vaccine failure: Susceptible to disease, despite following the appropriate dosing of the vaccine.
A baby was just born to a mother who is HBsAg positive, list three interventions that can reduce vertical transmission of hepatitis B?
- HB Immunoglobulin ASAP but within 12 hrs post birth- An IM dose of 0.5 mL HBIg
- HB Vaccine x 1 within 12 hrs post birth. 2nd dose @ 1 mo and 3rd dose @ 6 mo to complete the HB series
- Testing - Test for anti-HBs antibody and revaccinate if non-responder
List 4 conditions that must be met for vaccines to be considered interchangeable for a particular disease?
1) Vaccines must be authorized for the same indications and with equally acceptable schedules
2) Vaccines must be authorized for use in the same populations
3) Vaccines must contain comparable antigens
4) Vaccines must have similar safety, immunogenicity, efficacy
You are the MOH of Nunavut. Infants in Nunavut are disproportionately affected by Respiratory Syncytial Virus (RSV). The incidence rates, morbidity and mortality from RSV in infants are much higher in Nunavut compared to other areas. A community GP has emailed you advocating for universal screening of all infants of RSV.
List 5 criteria you will look at to decide if such program should be funded?
1) Principles for introduction of population screening (DTTS)
Disease
Is this condition an important health problem?
Do we have adaquate understanding of the natural history of the condition, including the development from latent to active disease?
Is there a recognizable latent stage or early symptomatic stage?
Test
Is there a suitable test or examination with high level of accuracy? (high sensitivity, high specificity, Positive Predictive Value, Acceptable to the population, minimal discomfort)
Is the test acceptable to the populatin?
Treatment
Is there an acceptable treatment for recognized disease?
Is there an agree-upon policy on whom to treat as patients?
System
- Are there facilities available for diagnosis and treatment?
- Is the cost of screening (including diagnosis & treatment) economically balanced against the cost of medical care as a whole?
- Is the population screening an on-going effort?
- are there programming support to ensure the target population get screened (e.g. reminders, registry, retention strategy, informed consent and proper follow-up and linkage to care?
You are the MOH of Nunavut. Infants in Nunavut are disproportionately affected by Respiratory Syncytial Virus (RSV). The incidence rates, morbidity and mortality from RSV in infants are much higher in Nunavut compared to other areas. A community GP has emailed you advocating for using a newly approved vaccine to vaccinate all infants.
What are some criteria you will look at to decide if such program should be funded?
ICEES FACED LEGS
Features of a good vaccine (ICEES)
Immunogenicity
Cost
Ease of administration
Effectiveness & preferabbly long-lasting immunity
Safety
Features of a good public health program (FACED LEGS)
Feasibility
Acceptability
Cost-effectiveness
Equitable
Disease burden
Legal
Ethical
clear Goals
good Strategy
You are an MOH in a regional PHU. A GP calls you to say he has a 35 yo patient with a rash who he suspects has measles.
A) Identify 5 elements of the case’s history and/or presentation that would assist you in determining the likelihood of this case being measles
B) List ONE laboratory test/specimen you would request the doctor order
The specimen comes back positive with measles
C) Who is considered a contact of a case with measles during their infectious period?
D) List 3 pieces of information you would use to assist in determining whether a contact of a measles case is susceptible
A)
- Is the case known to be previously vaccinated against measles or infected with measles?
- Is the case a contact of a known measles case or traveled to a measles endemic/outbreak area?
- What does the rash look like and where did it start then move to?
- What are the other accompanying symptoms/signs (e.g. cough, conjunctivitis, coryza, koplik spots)
- When did other symptoms occur in relation to timing of the rash?
B) Urine nucleic acid test
C) Anyone who shared the same air space with at the same time of the case and up to 2 hours case left the area
D)
- Year of birth (born before 1970 is considered immune)
- Documented evidence of previous vaccination against measles
- Laboratory evidence of immunity (previous infection or vaccination)
What are four communicable diseases that should be considered for screening for immigrants to Canada?
1) TB
2) HIV
3) HBV
4) HCV
5) Intestinal parasites (Strongyloides and Schistosoma)
What are 4 measures that are currently used to prevent HBV transmission at the population level in Canada?
- Universal HBV vaccination in childhood
- Screening of all pegnant women during pre-natal visits
- Screening of high risk populations e.g. IVDU, incarceration
- Harm reduction programs e.g. supervised consumption site and needle exchange
- Contact tracing and PEP of confirmed cases
- Screening of immigrants from countries with high incidence of HBV
You are the Chief Medical Officer of Health at Public Health Agency of Canada. You are considerating adding a new disease to the list of national notifiable disease list. What are some criteria you would consider to assess whether this new disease should be added?
Think Agent, Environment and Host: SICO? C-RN, CPR!
AGENT
Severity of the disease
Incidence of the disease
Communicability of the disease
Outbreak Potential
ENVIRONMENT
Changing patterns of disease over time
Regulatory programs (to inform and regulate certain programs such as immunization efforts)
Necessity for Public Health response
HOST
Cost of disease burden
Preventability
Risk perception of the public
In a study of COVID UK variant, it was determined that the probability of transmission per contact was 30% and the average infectious period was 10 days, and that cases had an average of 1.5 new contacts per day.
A) What is the R0
B) What immunity is required in the population to achieve herd immunity
C) You have vaccinated 80% of staff and residents in a LTCF with a total of 200 staff and residents. An outbreak occurs in this LTCF with 50 cases. 30 cases were unvaccinated and 20 cases had received the vaccine. What is the VE%?
D) Using the VE from (C), what proportion of the population needs to be vaccinated in order to achieve herd immunity?
A) R) = p x c x d = 0.4 x 1.5 x 10 = 5.25
B) Immunity = 1-(1/R0) = 1-(1/5.25) = 81%
C)
ARv = (20/160) x 100% = 12.5%
ARu = (30/40) x 100% = 75%
VE = (75-12.5)/75 x 100%= 83%
D) Coverage = Immunity/VE = 81/0.83 = 97.5%
You are an MOH in a regional PHU responsible for the TB program. One of the nurses reports to you they have an 8 yo child with a TST of 8mm
A) List 5 pieces of information you would request to help inform necessary recommendations/actions
You diagnose the child with latent TB and are selecting an appropriate regimen
B) List TWO key considerations when selecting a treatment regimen for latent TB
You decide to provide an isoniazid-only regimen for the appropriate time period, however, the child is reportedly malnourished.
C) Identify the supplement should be provided for the treatment and list the adverse effect it aims to prevent
D) List one other population group that should receive the supplement in (C) when receiving INH therapy
A)
- Is the child a contact of a known active TB case?
- Has the child previously had TB infection?
- Does the child have any changes on chest XRAY suggestive of active TB
- Does the child have an immunocompromising condition e.g. AIDS
- Is the child on any immunocompromsing medication e.g. chemotherapy
- Has the child previously received BCG?
- Is the child from a community with a high prevalence of active TB?
B)
- Ability/likelihood to comply with the treatment
- Potential side effects
- Contact of an active TB case with a form of drug resistant TB
- Age (older age increases hepatotoxicity risk of INH)
C) Pyridoxine (Vitamin B6) - perhipheral neuropathy
D) Pregnant women
List 2 possible causes of a
A) False positive TST
B) False negative TST
A)
- Nontuberculous mycobacterium infection
- Prior TB infection
- Previous BCG
B) Host, Procedural, Reader factors
- Poor immune response
- Improper injection/preparation/storage of tuberculin
- Reader error or reading at wrong point in time
You are MOH on call and receive a call of a surgeon who received a needlestick injury while operating on a person known to inject drugs.
A) List 5 pieces of information you would seek to inform your risk assessment
You decide HIV PEP is warranted
B) Within what timefram must HIV pep be commenced?
A)
- What type of needle was being used that caused the injury e.g. hollow-bore?
- Is the source’s blood-borne infection status known and if so, what is their viral load?
- How deep was the needlestick puncture?
- Does the injured have documented immunity to HBV?
- How long ago did the injury occur
B) HIV PEP - within 72 hours of exposure
List 6 steps in an outbreak investigation and management
1) Confirm Diagnosis & Verify existence of outbreak
2) Assemble a team including epidemiologist, PHN, (potentially PHI if associated with commercial food products) communication, AMOH
3) Case definition creation - to help with line listing to find more cases and do contact tracing
4) Data organized in terms of person, place and time for epidemiological analysis
5) Develop a hypothesis and evaluate the hypothesis by a case-control or cohort study if possible and revise hypothesis as needed
6) Implement control and revise control as needed
7) Established communication throughout the investigation and management and summarize the findings at the end and share learnings with others
List 4 essential elements of a case definition
- Person
- Place
- Time
- Clinical symptoms or signs or
- laboratory testing
List 3 characteristics of a disease that would make it amendable for eradition.
List the 6 steps of case management,.
- Confirm case: based on LTPPS – lab result, timing, person, place, symptoms
- Obtain TOCIS Hisotry - Travel, Occupation, Contacts before and after, Immunization Status, timeline of Symptoms
- Ensure case has received proper medical treatment
4. Advise to self-isolate and work exlusion if applicable
- Provide education and counseling about the disease, symptoms, public health meausres to take (e.g. hand hygiene, no food prep) and when to seek medical care.
- Contact tracing & notification - collect information about exposure to others during period of communicability
List the 5 phases of pandemic and 1 public health action associated with each phase
- Investigation - New discovery
- Alert national level health authority and WHO
- Aggressive case and contact management to detect all cases and their contacts
- Source identification
- Recognition - containment
- Communication of risk to public
- Rapid planning for wider transmission and pandemic
- Follow-up of identified cases and their contacts to prevent tranmission (containment strategy)
- Understanidng pathogen and public health action
- Initiation of a pandemic - mitigation
- Planning with health sector and other stakeholders
- Consideration for broader interventions
- Reduce the burden of health care resources e.g. setting separate place to test disease such as assessment centres
- Aceleration of a pandemic - mitigation with goal to attempt to slow down spread of sustained local tranmission
- Implement population interveiton e.g social distancing, universal masking, city-wide lock down.
- Advocacy for government investment in new treatment and vaccine
Deceleration of a pandemic wave
- Population health assement
- Recommendation about timeline of releaxing population public health measures (e.g. travel)