Infectious Disease Control and Public Health

• Public health is the science and art of preventing disease, prolonging life, and promoting human health through organized efforts and informed choices of society, organizations, public and private, communities and individuals
• Public Health Ontario (PHO) provides expert scientific and technical advice and support relating to infectious diseases, infection prevention and control, surveillance and epidemiology, health promotion, chronic disease and injury prevention, environmental and occupational health, emergency preparedness and incident response
• The Public Health Ontario Laboratory (PHOL) conducts 5.5 million tests per year and employs public health microbiologists for reference identification and public health support

Laboratory Functions of PHOL

• PHOL conducts primary testing for HIV and Hepatitis, Mycobacterium (e.g. TB), Zoonotic Diseases, Virology culture, Mycology, Parasitology, Water testing, and Food testing
• PHOL performs reference testing such as bacterial identification, antimicrobial susceptibility, confirmation of Level 3 Pathogens (e.g. TB), and Characterization of pathogens
• PHOL provides outbreak support by typing bacterial isolates, viral strain typing, fungal typing, and genome sequencing

Public Health Units

• There are 6 public health regions supporting local health programs with 34 PHUs in Ontario
• A public health unit is an official health agency established by a group of urban and rural municipalities to provide a more efficient community health program, carried out by full-time, specially qualified staff
• Health units administer health promotion and disease prevention programs to inform the public about healthy life-styles, communicable diseases control including education in STDs/AIDS, immunization, food premises inspection, healthy growth and development including parenting education, health education for all age groups and selected screening services
• The Medical Officer of Health (MOH) oversees each program
• Each is governed by a board of health, which is an autonomous corporation under the Health Protection and Promotion Act, and is administered by the medical officer of health who reports to the local board of health
• The board is largely made up of elected representatives from the local municipal councils, where the ministry cost-shares the expenses with the municipalities
• Public health units serve a defined geographic region/demographic and address specific health needs with a tailored public health system

Health Protection and Promotion Act (HPPA)

• The Health Protection and Promotion Act (HPPA) specifies the organization and delivery of public health, establishing the overarching legal framework, while regulations define the operational rules and codes, adapting to evolving public health needs
• Legislation is the overarching ‘law' voted in by the legislative branch, and typically does not change
• Regulation includes the processes that define the overall law (rules, codes, etc.) and is frequently updated/changes to meet the needs in public health
• Public health units gain oversight to deliver/ensure public health programs/services, while MOHs act in emergencies like epidemics, outbreaks, and infection control lapses

Public Health Nurses (PHNs)

• PHNs support public health programs, emphasizing primary prevention through vaccination via community immunization/influenza clinics, sexual health education, prenatal classes for infection prevention, and active/passive immunization for contacts of cases (HAV, meningitis)
• PHNs support PH programs by conducting secondary prevention through active disease screening such as TB and STIs while also case finding of diseases like flu or COVID19.
• PHNs engage with outreach investigation and epidemiology tracing, rabies(along with CFIA), and reporting notifiable diseases to MOH

Core functions of public health labs/units

• Communicable disease surveillance, prevention and control
• Outbreak and emergency response to communicable diseases
• Environmental health and food safety
• Reference testing, specialized screening and diagnostic testing
• Biosafety, containment, and biohazard spill response programs
• Integrated communicable disease data management
• Public health policy development and evaluation
• Laboratory improvement and regulation (QA)
• Training and education of health care and public health workers
• Public health related research and development
• Reportable diseases include blood-borne viruses, STIs, GI, 'severe' diseases (e.g. Ebola), and vaccine = preventable diseases

Public health surveillance

• Public health surveillance uses individual encounters with healthcare providers resulting in clinical or lab diagnoses (first point of contact), surveys, etc.
• Surveillance involves continuous, systematic collection, analysis, and interpretation of health-related data for planning, implementing, and evaluating public health practices
• Surveillance serves as an early warning system for impending public health emergencies, documenting intervention impact and progress towards goals; monitors/clarifies epidemiology, prioritizing/informing policy

Organizational Clusters

• There are 3 clusters of PH organizations in Canada (continuously exchange info to help support the public health):
• Local/regional – local actions, policies and programs developed in collaboration with others
• Provincial/territorial - P/T actions, policies and programs developed in collaboration with others
• National - Federal actions, policies and programs developed in collaboration with P/T authorities and others

Mumps characteristics

• Mumps is caused by an RNA paramyxovirus, is transmitted via droplets, direct contact with saliva, or indirect contact with contaminated surfaces
• Mumps has an incubation period of 12-25 days and a communicability period from 2 days before to 5 days after symptom onset
• Mumps symptoms include fever, headache, malaise, myalgia, and parotitis, with 20% being asymptomatic and 50% having non-specific respiratory symptoms
• Mumps is tested using serology (antibodies) and molecular (PCR) testing (virus); prevented with 2 doses of MMR vaccine (76-95% effective)

Mumps Specimen Collection

• Buccal swabs may be taken up to 9 days after symptom onset by massaging the parotid gland area and swabbing the Stensen's duct near the upper rear molars
• Throat swabs can be taken up to 9 days from symptom onset and are less reliable after 9 days
• Urine can be collected up to 14 days following symptom onset (minimum vol require: 5.0 ml). Virus in urine detectable longer due to tissue differences
• CSF testing may be performed in cases of aseptic meningitis (minimum vol required: 1.0 ml)

What happens when a case is identified

• When a case is identified the lab or physician reports notifiable result to PHU (legal requirement of HPPA)
• The PHU nurse will collect report and enter available lab/clinical data into Integrated Public Health Information System (iPHIS; legal requirement of HPPA)
• The PHU nurse will initiate patient contact/counseling, perform contact tracing, and engage in additional fact finding (i.e. descriptive epidemiology e.g., timing/place of potential exposures, risk factors, etc.)

Key definitions for communicable diseases

• Outbreak: Occurrence of cases exceeding normal expectations in a specific time and place
• Index case: First identified case at the start of an outbreak
• Reproductive rate (R0): Average new cases from one case during the infectious period (mumps R0 = ~4-7 = ~4-7 people infected)
• Attack rate: Proportion of at-risk population contracting the disease (ex: 50% attack rate = 50% of the population to be infected in 2025)
• Eliminated disease: Reduction to zero incidence in a defined area through deliberate efforts (Ex: mumps in Canada - but reintroduction is possible)
• Endemic disease: Uninterrupted transmission chain for over one year
• Imported case: Confirmed case acquired outside of Canada
• A case definition describes criteria for person (age, sex, ethnicity, occupation, exclusion criteria), place (specific geographic location), time (period of exposure), and clinical features (signs/symptoms) associated with a particular infectious disease/OB

Descriptive Epidemiology

• MOH and LTCH maintains case definitions - sometimes federal/provincial definitions vary
• Confirmed case: Lab confirmation with compatible signs/symptoms, w/o recent mumps-containing vaccine (7-42 days)
• Defined by isolating the mumps virus, detecting mumps virus RNA, Seroconversion or significant rise in mumps IgG titre, or detecting mumps immunoglobulin M (IgM) antibody in a person who is either epidemiologically linked to a lab-confirmed case or has recently travelled to an area of known mumps activity
• Probable case includes clinically compatible signs and symptoms, but without lab tests or epidemiological link

Managing an Outbreak/Pandemic: Key Questions include:

• What are we confronting, its origin, and testing methods?
• How do we recognize and contain the disease (clinical presentation, incubation/communicability periods)?
• What is the transmission mechanism (reproductive/attack rates)?
• What countermeasures are possible?
• SARS-CoV-2: Virus (2019-nCoV); COVID-19: Disease

SARS-CoV-2 and Other Corona Viruses

• Belongs to Nidovirales order and Coronaviridae (family)
• (ortho) Coronovirinae (sub-family) includes Alpha/Beta (mammals) and Gamma/Delta (birds) includes four common cold coronaviruses: OC43, NL63, HKU1, 229E
• SARS-CoV-2 is 7th coronavirus infecting humans, adapting to become endemic, resembling normal flu symptoms.
• The receptor for SARS-CoV-2 (tissue tropism) = early phylogenetic evidence suggests angiotensin converting enzyme-2 (ACE2)
• ACE2 is distributed throughout the body and notably found on Type II pneumocytes (83%0 – pharynx, larynx, alveolus, macrophages) and the Endothelium
• It explains widespread dissemination of disease and is a potential guide for therapeutics

COVID-19 Infection & Progression

• SARS-CoV-2 enters through mucous membranes (nasal epithelia), or infects respiratory epithelial cells.
• Extensive alveolar damage, bilateral edema, type II pneumocyte hyperplasia, thickened alveolar septa, and inflammation
• Causes typical kidney changes like tubular injury, loss of brush border integrity, endothelial damage, and capillary occlusion

COVID-19 Disease Factors

• Max incubation period of 14 days (median = 4-5 days post-exposure)
• Symptoms vary by person/age (influenza-like illness), including common symptoms (fever, cough, shortness of breath)
• Severe symptoms are shortness of breath/, chest pain/pressure, and loss of movement/speech
• Multisystem inflammatory syndrome in children (MIS-C); 20-75% of people infected will be asymptomatic
• Risk factors for sever disease include: age, hypertension, obesity, diabetes
• Once it starts to migrate to lower respiratory tract, it becomes more mild to moderate
• Severe pneumonia is caused by SARS-CoV-2 caused by immune system dysfunction, macrophage activation, hypercytokinemia and coagulopathy
• Inflammatory Response is prolonged and overactive
• Common symptoms include fever, dry cough, fatigue, and other symptoms include headache, loss of smell, nasal congestion, coughing up sputum, and SOB.
• Severe symptoms include: difficulty waking, confusion, bluish face or lips, coughing up blood, and kidney failure

Ontario Case Definitions (COVID-19)

Ontario Case Definition - Probable COVID-19 Cases

• Symptoms compatible with COVID-19 and not lab tested and has either high-risk or close contact exposure, or was exposed to a known cluster/outbreak of COVID-19
• A person who is asymptomatic, with diagnosis of COVID-19 inconclusive.
• If no symptoms and high-risk or close contact

Ontario Case Definition – Confirmed COVID-19 Cases

• Cases must have a laboratory confirmation w/ positive nucleic acid amplification test or point-of-care NAAT deemed acceptable by the Ontario Ministry of Health.
• Demonstrate seroconversion or diagnostic rise (at least 4-fold or greater from baseline) in viral specific antibody titre
• Molecular tests may still yield positive results due to detection of non-active nucleic acids, even after the patient has cleared the active virus.
• A previous case with subsequent confirmed infection, supported includes genome sequencing or VOC in dPCR

COVID testing

• RAT = Rapid Antigen Test and may miss something early
• NAAT = nucleic acid amplification test

Ct Values

• The lower the Ct, the higher viral load.
• Ct value goes up, viral load goes down
• It takes less cycle since you have a higher load at the beginning
• Transmission occurs 48 hours proor to symptom onset (presymptomatic) to up to 10 days post-symptom onset changing with population immunity (e.g., 5days)
• 40-50 precent transmissibility
• Asymptomatic cases in 0-80%
• Transited via direct (e.g., saliva) or indirectly (e.g., fomites) through: respiratory droplets (large), and aerosols (small) from cough, sneezes, sings, shouts, or talks
• Risk depends on load, risk factors, PPE, distance, size, air changes, indoors/outdoors
• COVID less likely to be airborne spread but still possible; less likely depending on factor, droplets have higher risk of transmission

COVID -19 interventions

• Decrease transmission, decrease ICU bed occupancy, decrease strain on healthcare resources
• Public health restrictions are effective only when followed
• Epidemiological Reading, Vaccines ect Re reflects

COVID-19 Variants of Concern

• VOCs have mutations, require sequencing, and are 50-75% more transmissible
• Vaccines are expected to be effective
• Omicron mutations are more infectious, evasive, and are identified to be more contagious, less severe, immune

Omicron facts

• 2x ancestral strains
• The Delta variant R0 5.08; Omicron variant 4.2x more infectious
• Infections: 91% less fatal than delta variant, 51% less likely to Hospitalized for
• Common symptoms: cough, fatigue, congestion, runny nose headaches, sore throat
• Omicron infects and multiplies by 70 and in the upper air way
• Omicron is 60 times more mutated
• Public Health 'Trigger points'
• Use the positive rate; case count as primary

COVID Isolation:

Isolation Period

• If residence , hospital and immunocompromised
• 10 Days, can be modifeid by a physician. Symptom should be improving.

Additional Precautions after Self Isolation

• N/A

Population Isolation Period

• All other individuals not listed above who have COVID-19 symptoms OR a positive COVID-19 test
• Until symptoms have been improving for 24 hours is gastrointestinal symptoms and no fever present.
• Asymptomatic individuals with a positive test result do not need to self-isolate unless symptoms develop. If symptoms develop, they should

Additional Precautions and self isolation

• 10 days
• Monitor For 10 days self isolate if symptoms develop
• Wear mask in public setting
• test based clearance NOT routinely recommended

Explores the significance of the effective reproductive number (Re) being below 1 and how public health trigger points shifted during the COVID-19 pandemic. It also covers Omicron variant characteristics, the role of unvaccinated populations in variant emergence, and appropriate actions following high-risk exposure.