Module 5.2 Flashcards
Introduction to Viruses
Viruses are obligate infectious agents (can only replicate in living cells).
Each virion has a protective outer layer (envelope) and genetic material (genome).
Viruses aren’t considered living organisms (no cells, growth, or energy production).
In humans, viruses cause a range of illnesses from mild (e.g., common cold) to severe.
Viruses constantly mutate and evolve, leading to new strains.
Many viruses originate in animals (e.g., birds, pigs, bats) and may jump to humans (e.g., Influenza A).
what do viral cycles start with
attachment to host receptor protein which then grants them access to the inside of the cell
Structure of a Viral Particle
Viruses come in various shapes and sizes.
They contain single or double-stranded DNA or RNA as their genome.
Surrounded by a capsid (protein coat), some viruses have an outer envelope derived from the host cell membrane.
The outer layer (capsid or envelope) contains viral proteins that interact with receptor proteins on host cells.
This interaction allows the virus to attach to the host cell and enter it.
what must viruses do to cause disease
replicate
different mechanisms for viruses to enter cell
uncoating and synthesizing its genome, translating
The 1918 Influenza Pandemic
Both bacteria and viruses can cause infectious diseases.
Pandemics and epidemics occur when infection rates become uncontrollable.
The last major pandemic occurred in 1918, caused by an influenza virus.
WHO and other public health agencies have studied the 1918 pandemic to understand and better manage future pandemics.
Similar to COVID-19, the 1918 influenza had several waves of infection, with the second wave being especially lethal.
The virus spread in three waves and eventually evolved into the annual influenza seasons seen worldwide today.
Death Toll of the 1918 Influenza Pandemic
The 1918 influenza pandemic caused 50-100 million deaths worldwide.
⅓ of the global population contracted the influenza virus.
At the time, little was known about the disease, making it difficult to manage.
The origins of the virus are still unknown.
Unexpected deaths were common among young, healthy adults (ages 20-45).
One theory suggests that an overactive immune response in young adults led to secondary pneumonia and tissue damage, which contributed to the high mortality rate.
1918 Epidemic in Canada
Influenza virus entered Canada through eastern ports (Quebec City, Montreal, Halifax).
Troop movements spread the virus across the country.
No quarantine measures for domestic travel.
Local authorities prohibited gatherings and isolated the sick, but measures failed.
Canada struggled due to lack of coordination and resources.
The Department of Health was founded in 1919 in response.
The Impact of 1918 on Health Inequities in Canada
In 1918, medical treatment was only available to those who could afford it.
Poor, non-white, and Indigenous patients were often segregated to poorly staffed areas.
Many had to work through illnesses to afford basic needs.
Loss of parents led to children leaving school to work.
Deaths from influenza were high among Indigenous populations:
6.2/1000 non-Indigenous Canadians died.
Indigenous death rates ranged from 10.3 to 61 per 1000 in different regions.
In Okak, an Inuit village, 204/263 people died.
How and Indigenous Community Protected Itself
Influenza devastated remote Indigenous communities along the Pacific coast of the US and Canada.
In western Alaska, 30-95% of the population in some communities died within a week.
Some remote communities avoided the virus entirely.
Shishmaref, an island north of the Bering Strait, prevented the outbreak by stationing guards to restrict entry and exit, protecting other nearby communities.
what is covid caused by
the SARS-CoV-2 virus.
SARS-CoV-2 Mechanism of Infection
Entry: Virions enter the body via the nasal/oral passages, traveling to the lungs.
Attachment: SARS-CoV-2 attaches to ACE2 receptors on lung cells using its spike protein.
Replication: The virus hijacks host cell machinery to replicate.
Release: New virions bud out of the host cell.
Infection: Virions spread to other tissues and may infect others if expelled.
SARS-CoV-2 symptoms
Dry cough, tiredness, fever
Mild cases: loss of smell and taste
Brain fog has also been reported in some patients which persists months after infection is cleared
Pandemic Timeline and Global Spread
Dec 2019: First pneumonia cases reported in Wuhan, China.
Jan 2020: WHO publishes outbreak news; China shares SARS-CoV-2 genetic sequence.
Mar 2020: WHO declares COVID-19 a pandemic; lockdowns and border closures implemented worldwide.
Types of Variants and Mutation Classifications
of covid
Variant Under Monitoring (VUM): Potential impact on virus behavior but no strong evidence of epidemiological effect.
Variant of Interest (VOI): Increased transmissibility or immune evasion, but not yet a major public health threat (e.g., BA.2.86, JN.1).
Variant of Concern (VOC): Significant public health risk (e.g., Alpha, Beta, Gamma, Delta, Omicron).
As of March 2023, no new variants have been classified as VOCs.
Virus Genome and Structure
of covid
Structural proteins: spike, envelope, membrane, nucleocapsid
Non-structural proteins (NSPs): involved in replication
Spike protein: crucial for entry into human cells, targeted by vaccines, and undergoes conformational changes when binding to ACE-2 receptor.
Mutations in the spike protein affect viral transmissibility, immune evasion, and vaccine efficacy.
Impact of vaccines on Cases and Deaths
Before vaccines: High mortality, especially among older adults and vulnerable groups.
Vaccination campaigns (2021): Helped reduce deaths despite Omicron surges.
Post-vaccine: Cases rose with new variants, but deaths stayed lower due to vaccine protection.
Early Waves of Infection covid
Wave 1 (Mar 2020): Initial outbreak, severe impact on long-term care facilities.
Wave 2 (Sept 2020 – Early 2021): Higher transmission during colder months.
Wave 3 & 4 (Spring – Summer 2021): Alpha and Gamma variants, increased lockdowns.
Wave 5 (Winter 2021-2022): Omicron BA.1 causes surge but lower mortality due to vaccines.
Wave 6 & 7 (Spring – Summer 2022): Omicron BA.2 and BA.5 dominate.
Variant Evolution Over Time of covid
Pre-2021: Original SARS-CoV-2 strain was dominant.
Early 2021: Alpha, Beta, and Gamma variants emerge.
Mid-2021: Delta variant becomes dominant, increasing hospitalizations.
Late 2021 – 2022: Omicron replaces Delta, leading to waves of infection.
2023 – 2024: JN.1 and its descendants (KP, KS, and LB strains) dominate.
COVID-19 Infection Control
SARS-CoV-2 Spread: Spreads via droplets and aerosols; doesn’t survive long on surfaces.
Measures to Stop Spread:
Distancing: Maintain 2-meter social distance.
Closures: Close high-contact areas/activities.
Masking: Wear masks and shields.
Washing: Wash hands, sanitize, clean surfaces.
Staying Home: Stay-at-home orders to limit spread.
Quarantining: Isolate travelers, symptomatic individuals, and close contacts.
Tracing: Track infected individuals and contacts.
Cindy Mitchell
covid survivor
46 yo nurse from Napanee ontario
Caught COVID in spring 2021
Extremely sick for two weeks and visited emerg multiple times, got admitted to KGH in COVID-19 ward.
pandemics and vulnerable populations
Elderly and Medically Unwell: High fatality rates in long-term care, impacting mental and physical health.
Low Socioeconomic Status: Job loss and high-risk work without paid sick leave or testing.
Racism and Discrimination: Asian communities, particularly Chinese, faced ostracization.
Mental Health and Addiction: Loss of social support and healthcare services.
Food Insecurity: Increased, with disrupted school food programs in countries like Canada, the U.S., and the UK.
pandemic and Healthcare Disruptions
Delayed Medical Care: Routine screenings and exams were postponed.
Limited Access to Care: Shift to telehealth led to missed diagnoses.
Insurance Issues: Job loss caused loss of health insurance, especially in non-universal healthcare systems like the U.S.
pandemics and living conditions and workplace risks
High-Density Housing Risks: Multi-unit dwellings saw higher infection and death rates.
Frontline Workers: Manufacturing, agriculture, and food production workers faced higher exposure with limited protective equipment and time off.
