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Infectious Diseases and Public Health: Review Flashcards

Pandemic, epidemic, endemic, outbreak, sporadic

  • Pandemic: infection/disease outbreak that spreads worldwide; not confined to a single country.
  • Epidemic: a wider-than-usual occurrence within a region or population.
  • Endemic: disease consistently present in a given area or population; example: seasonal flu or common cold.
  • Outbreaks: localized clusters of cases within a region.
  • Sporadic: random, isolated cases in scattered locations (e.g., a few cases in one state or country).
  • Graphical representation (time vs. number of cases):
    • Endemic baseline sits at a relatively steady level.
    • Epidemic shows a sharp rise (peak) in a given period.
    • Pandemic shows a broad, global rise across regions.
  • Historical patterns (countries and time): not everything is purely local; many diseases spread through travel, trade, and vectors.

Historical infectious diseases and vectors

  • Plague (Yersinia pestis):
    • Vector: fleas on rodents; transmission to humans via bite of infected fleas. Rodents (rats, mice) are reservoirs.
    • Pathogen naming example: genus first, species second, both italicized with genus capitalized: extit{Yersinia extit{ pestis}}.
    • Clinical progression: buboes (swollen lymph nodes) due to lymphatic system involvement; after entering the bloodstream, the infection can affect the respiratory system and spread between people.
    • Historical note: plague caused high mortality in Europe during the Middle Ages (often cited as 10–90% mortality in some outbreaks).
  • Smallpox:
    • Causative organism: virus (not bacteria).
    • Vaccination history and eradication context are touched upon; vaccination campaigns contributed to eradication.
  • Naming conventions for microorganisms (microbiology basics):
    • Genus is capitalized; species is lowercase and italicized.
    • Example: extit{Yersinia extit{ pestis}}; the genus name is capitalized and the species name is lowercase and italicized.

Basic immunology and anatomy references mentioned

  • Lymphatic system overview: lymph nodes (lymphoid tissue) house immune cells; lymphatic vessels transport immune cells and fluids.
  • Immune response to a pathogen bite (e.g., plague): immune activation leads to lymph node enlargement (buboes).
  • Immunology terminology reminders (as discussed):
    • Antigen: a molecule that triggers an immune response.
    • Antigenic: related to antigens triggering an immune response; changes in antigens can affect immunity.
  • Note on a common misstatement in the transcript:
    • Aseptic technique is defined in textbooks as keeping something free from contamination by pathogens. The transcript includes a moment where the instructor’s explanation appears inverted. Correct: aseptic means free from contamination; contamination is contrary to aseptic principles.

Measles (Rubeola)

  • Causative agent: measles virus (a virus; not bacteria).
  • Transmission: respiratory droplets (highly contagious).
  • Clinical features: high fever, cough, coryza (runny nose), conjunctivitis (red, watery eyes); Koplik spots (small white spots) on the oral mucosa.
  • Surface stability: measles virus can survive on nonliving objects for up to 2 hours.
  • Vaccination and prevention: measles vaccine is part of the MMR vaccine; prevention through vaccination is essential.
  • Vaccine schedule (as discussed): first dose at 12 ext{-}15 ext{ months}; second dose later (school entry) to ensure immunity.
  • Case scenario connection: differentiate measles from other infections by characteristic Koplik spots and the pattern of cough, fever, and rash.

Influenza (flu)

  • Causative agents: influenza viruses types A, B, and C.
  • Type A characteristics: primarily responsible for epidemics and pandemics; has multiple hosts (humans and animals).
  • Antigenic factors and surface proteins:
    • Hemagglutinin (H) and neuraminidase (N) surface proteins; subtypes named as HxNy (e.g., H1N1, H5N1, H3N2).
    • The lecture references multiple RNA strands/segments in the influenza genome for variability; the concept is that these viruses can mutate via genetic reassortment. The diagram in the talk showed several RNA segments (numbers like 9 and 11 were mentioned) to illustrate variability. Note: in reality, influenza A has a segmented genome with 8 RNA segments; the genome segmentation enables reassortment and rapid antigenic change.
  • Specific historical example: 2009 H1N1 “swine flu” outbreak discussed as an example of a pandemic origin from animal-to-human transmission followed by human-to-human transmission.
  • Antigenic changes:
    • Antigenic drift: gradual mutations in surface proteins that may require vaccine updates.
    • Antigenic shift: major changes in surface antigens, potentially causing epidemics or pandemics due to novel strains.
  • Vaccination and vaccine composition (as discussed):
    • The term “trivalent” vaccine given in the talk:
    • Two influenza A strains (the talk mentions H1N1 and H5N1 in the example) and one influenza B strain.
    • In practice, current formulations may be quadrivalent (two influenza A strains and two influenza B strains).
    • Vaccination and immune response timing: vaccines do not confer immediate protection; antibody development takes about two weeks to reach protective levels.
  • Preventive measures and symptom management: handwashing remains a basic preventive measure; treatment focuses on symptom relief (e.g., analgesics like acetaminophen/NSAIDs).
  • Vaccine technology notes from the talk:
    • mRNA vaccines have been developed and used for COVID-19; discussion includes the concept of spike protein targeting and rapid vaccine development due to prior research.
    • Discussion of vaccine development approaches: whole-cell, subunit, toxoid, and genetic (DNA/RNA) vaccine concepts.
  • Flu surveillance: a CDC link is mentioned to track current cases during flu season.

Vaccines: types, history, and concepts (as discussed)

  • Vaccine development taxonomy:
    • Whole-cell vaccines: use the entire organism, either inactivated (killed) or attenuated (disabled).
    • Subunit vaccines: use specific components of the organism (e.g., toxins, surface proteins) rather than the whole organism.
    • Toxoid vaccines: inactivate bacterial toxins to elicit immunity without disease-causing toxin activity.
    • Acellular vaccines: a refined version of subunit vaccines that include only certain antigenic components (e.g., acellular pertussis – DTAP vs whole-cell pertussis).
    • DNA vaccines: use DNA encoding antigenic proteins; RNA vaccines: use mRNA encoding antigens (spike proteins, etc.). The talk notes that DNA vaccines have had mixed success; RNA vaccines have been prominent in recent vaccine development (including COVID-19).
  • Pertussis vaccine specifics (as discussed):
    • DTaP stands for Diphtheria, Tetanus, and acellular Pertussis.
    • AP in DTaP refers to acellular pertussis (not the whole cell).
    • Historical note: older whole-cell pertussis vaccines had more adverse effects; replacement with acellular formulations aimed to reduce side effects while preserving immunity.
  • Pregnancy and vaccination timing:
    • Vaccination during pregnancy: avoid certain vaccines in the first and second trimesters; timing depends on the vaccine and risk assessment (the talk mentions caution around trimester windows).
    • For adults caring for infants, a pre-exposure vaccination update is recommended at least two weeks prior to contact to allow protective antibody levels to develop.
  • Public health rationale for vaccines:
    • Herd immunity: when a high proportion of the population is vaccinated (~often cited as 75–80% or higher), unvaccinated individuals gain protection due to reduced transmission.
    • The talk connects herd immunity to reducing the spread of disease within populations.
  • Pediatric vaccination and school entry: schedules and school notification processes related to vaccination status are discussed.
  • General vaccine-related public health themes from the talk:
    • The ongoing debate around vaccines is acknowledged; the speaker emphasizes focusing on evidence-based information.
    • Public health infrastructure and funding (NIH) implications are discussed (see the section on Emerging and Reemerging Diseases below).

Emerging and reemerging infectious diseases

  • Definitions:
    • Emerging infectious diseases: diseases that are newly appearing in a population or previously unknown.
    • Reemerging: diseases that existed but are increasing in incidence or geographic range again.
    • Global vs. local emergence: some diseases emerge in the US, others emerge abroad and then appear in the US due to travel and trade.
  • Case examples mentioned in the talk (illustrative, not exhaustive):
    • Ebola: described as global, with occurrences linked to travel and healthcare settings; treated in the talk as not a primary focus for testing in this session.
    • Dengue fever, West Nile virus, chikungunya: vector-borne diseases; transmission through mosquitoes; global spread linked to travel, trade, and climate factors.
    • Chikungunya: highlighted as spreading rapidly; note on the global presence and vector biology.
    • Zoonotic and vector-borne considerations: many diseases involve vectors (mosquitoes, ticks) and animal reservoirs.
  • Transmission and control framework:
    • Mode of transmission determines control strategies (e.g., mosquito control for dengue/chikungunya, tick avoidance for Lyme disease, rodent control for plague).
    • Examples provided: rodent/ flea control for plague; personal protective measures (long sleeves, pants, tucked-in socks, DEET) for tick-borne diseases.
  • Ecological and societal factors driving emergence:
    • Ecological changes (deforestation, habitat alteration) can increase contact with wildlife reservoirs.
    • International travel and commerce enable rapid cross-border spread of pathogens.
    • Technology, industry, and microbial adaptation (mutations) contribute to emergence.
    • Public health infrastructure and surveillance gaps can hinder detection and response.
  • Four main goals of the 1995 global initiative on emerging infections (CDC/WHO collaboration):
    • Surveillance and reporting
    • Deployment of trained personnel for outbreak response
    • Increased funding for research
    • Prevention and control measures
  • Funding and policy context mentioned:
    • NIH funding cuts were discussed (e.g., a referenced figure around 580{,}000{,}000), highlighting concerns about research and public health capacity.
  • Case-based testing framework described by the instructor:
    • Focus on three key elements for each infection: causative organism, mode of transmission, and control.
    • Emphasis on using study guides and prior-lecture content to prepare for exams.
  • Notable case and testing caveats from the talk:
    • The instructor notes that not everything covered in lectures will be tested; focus is on the study guide and core concepts (causative organism, transmission, control).
    • Quizzes are used to reinforce learning and reduce last-minute cramming; quizzes count toward the grade and help with spaced learning.
  • Other pathogens and topics touched upon (briefly):
    • Chlamydia trachomatis: a sexually transmitted bacterium; symptoms in both sexes; risk of infertility due to blockage of fallopian tubes; screening and treatment importance; potential for ectopic pregnancy if tubal damage occurs.
    • Bordetella pertussis: cause of whooping cough; respiratory droplet transmission; high-risk groups include young children; vaccination with DTaP/AP; discussion of vaccine development history (whole-cell vs acellular).
    • Staphylococcus aureus and MRSA: hospital-acquired infection; range from pimples to deep abscesses and septicemia; transmission through contact; importance of aseptic technique and not sharing personal items; tampon-associated toxic shock syndrome history noted as a cautionary point.
    • Lyme disease (Borrelia burgdorferi): tick-borne bacterial infection; stages include early flu-like symptoms, possible bull’s-eye erythema migrans; potential cardiac and neurological complications; prevention via protective clothing and DEET; tick checks after exposure; nymphal ticks are particularly infectious due to their small size.
    • Cryptosporidium parvum and cryptosporidiosis: a protozoan parasite causing watery diarrhea via ingestion of contaminated water; transmission via fecal-oral route; oocysts shed in feces; notable for hospital-acquired cases in immunocompromised patients; treatment is mainly supportive; resistant to many drugs due to eukaryotic nature of the organism; control based on transmission route (water safety, hygiene, pool safety).
    • Giardia and other protozoa (contextual mentions): noted for different transmission modes and health impacts in immunocompromised hosts.
  • Practical implications and applications highlighted by the talk
    • Importance of identifying causative organisms, transmission routes, and effective control measures for each infection to guide prevention and management.
    • Practical infection-control recommendations (hand hygiene, surface disinfection, isolation of infected patients, avoiding sharing personal items).
    • The role of vaccination and herd immunity in preventing outbreaks and protecting vulnerable populations.
    • The need for robust public health infrastructure, surveillance, and research funding to prevent and control emerging and reemerging infections.
  • Educational framing and study strategies (as described by the instructor)
    • Emphasis on study guides and explicit testing focus: definitions, causative organisms, transmission, and control
    • Use of quizzes to promote ongoing study and spaced learning rather than last-minute cramming
    • Encouragement to connect new material to foundational principles (e.g., cell biology, immunology, epidemiology) and real-world relevance

Key definitions and quick references (glossary-style)

  • Causative organism: the specific pathogen responsible for a disease (e.g., extit{Yersinia extit{ pestis}} for plague; measles virus; extit{Borrelia burgdorferi} for Lyme disease; MRSA is a resistant strain of Staphylococcus extit{ aureus}).
  • Mode of transmission: how a pathogen spreads (e.g., respiratory droplets, fecal-oral, vector-borne like fleas or ticks, direct contact).
  • Control measures: strategies to prevent transmission and infection (e.g., rodent/vector control, vaccination, handwashing, surface disinfection, safe sex practices, screening programs).
  • Herd immunity: population-level protection when a large portion of individuals are vaccinated or immune, reducing transmission to unvaccinated individuals. Often modeled as H
    ange ext{approximately } 1 - rac{1}{R0}, where R0 is the basic reproduction number.
  • Antigen and antigenic concepts:
    • Antigen: a substance that triggers an adaptive immune response.
    • Antigenic shift: major changes in surface antigens (often via gene reassortment) leading to new strains and potential epidemics/pandemics.
    • Antigenic drift: gradual accumulation of mutations in antigens, leading to gradual immune escape and possibly requiring vaccine updates.
  • Vaccine types (brief):
    • Whole-cell vaccines (killed or attenuated organisms)
    • Subunit vaccines (specific components of the organism)
    • Toxoid vaccines (detoxified toxins)
    • Acellular vaccines (subunit components with fewer side effects)
    • DNA vaccines (DNA encoding antigens)
    • RNA vaccines (mRNA encoding antigens; e.g., spike protein for viruses)
  • Terminology corrections (noted in lecture):
    • Aseptic technique: intended to keep areas free from contamination by pathogens; essential for reducing infections in clinical settings.
    • Prokaryote vs eukaryote distinction (brief): eukaryotes (e.g., human cells, many protozoa) have true nuclei (karyon); prokaryotes lack a true nucleus; these concepts underpin many differential treatments and antibiotic strategies.

Connections to broader biology and public health relevance

  • The material links microbiology to epidemiology, showing how pathogen biology (host range, transmission routes, environmental stability) shapes outbreak dynamics and control strategies.
  • Vaccination science connects molecular biology (antigen structure, immune recognition) to population health outcomes (herd immunity, vaccination schedules).
  • Public health strategy integrates surveillance, workforce capacity, research funding, and prevention programs to mitigate both established infections and emerging threats.
  • Ethical, philosophical, and practical implications touched upon via discussions of vaccination controversies, policy decisions, and the balance between individual rights and community protection.

Quick study prompts (based on the transcript)

  • Define and give examples of pandemic, epidemic, endemic, outbreak, and sporadic.
  • Explain how the plague is transmitted and what anatomical system is involved in the progression from buboes to systemic infection.
  • Name the causative organisms for measles, influenza, pertussis, Lyme disease, chlamydia, MRSA, and Cryptosporidium parvum (as described in the lecture).
  • Describe three modes of transmission and give one control strategy for each.
  • Explain the difference between whole-cell, subunit, toxoid, and acellular vaccines, with examples.
  • What is an antigen, and what is meant by antigenic shift vs drift?
  • What are Koplik spots, and what disease are they associated with?
  • What are the standard vaccination timing recommendations mentioned for measles and for adults caring for infants?
  • Summarize the four goals of the 1995 CDC/WHO initiative on emerging infections.
  • What funding concerns about NIH were raised in the lecture, and why is funding relevant to outbreak readiness?

Notes on exam-ready framing (from the transcript)

  • For any infectious disease discussed, be able to answer succinctly:
    • Causative organism
    • Mode of transmission
    • Control measures
  • Expect case-based reasoning: given a clinical scenario, identify the most likely infection based on presentation (e.g., fever, rash, exposure history) and reason through the causative organism and transmission route.
  • Be prepared to discuss vaccine mechanisms (whole-cell vs acellular vs toxoid vs mRNA/DNA vaccines) and how these relate to safety and immune response.
  • Expect questions about the difference between emerging and reemerging infections, including real-world examples and the public health factors that drive them.

Summary takeaway

  • Infectious diseases vary widely in causative organisms, transmission routes, and control strategies. Understanding these core factors—causative organism, mode of transmission, and effective control—enables optimal prevention, timely outbreak response, and informed vaccination decisions. The lecture threads together clinical features, microbiology fundamentals, immunology concepts, and public health policy to illustrate how science translates into protecting population health.