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Questions and Answers
What is a key characteristic of acute viral infections?
What is a key characteristic of acute viral infections?
Which of the following is true about chronic infections?
Which of the following is true about chronic infections?
How are slow viral infections characterized?
How are slow viral infections characterized?
Which of the following viruses is best known for causing chronic infections?
Which of the following viruses is best known for causing chronic infections?
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What distinguishes persistent infections from acute infections?
What distinguishes persistent infections from acute infections?
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What term describes a disease that is easily spread from one host to another?
What term describes a disease that is easily spread from one host to another?
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Which term refers to the fraction of a population that contracts a disease during a specific time?
Which term refers to the fraction of a population that contracts a disease during a specific time?
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What is a key characteristic of a chronic infection?
What is a key characteristic of a chronic infection?
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Which type of disease is consistently present in a population?
Which type of disease is consistently present in a population?
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Which of the following best describes a slow viral infection?
Which of the following best describes a slow viral infection?
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What does the term 'pandemic disease' refer to?
What does the term 'pandemic disease' refer to?
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What defines a communicable disease?
What defines a communicable disease?
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What best describes the process of acute disease development?
What best describes the process of acute disease development?
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Which description best fits a chronic disease?
Which description best fits a chronic disease?
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Which type of infection involves symptoms that are between acute and chronic?
Which type of infection involves symptoms that are between acute and chronic?
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What does the term 'focal infection' refer to?
What does the term 'focal infection' refer to?
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Which of the following is NOT a method of disease transmission?
Which of the following is NOT a method of disease transmission?
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What is the main vehicle for direct contact transmission of pathogens?
What is the main vehicle for direct contact transmission of pathogens?
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Which type of disease is characterized by a period of no symptoms when the causative agent is inactive?
Which type of disease is characterized by a period of no symptoms when the causative agent is inactive?
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What characterizes vertical transmission of pathogens?
What characterizes vertical transmission of pathogens?
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Which statement best describes zoonoses?
Which statement best describes zoonoses?
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What is meant by 'mechanical transmission' regarding vectors?
What is meant by 'mechanical transmission' regarding vectors?
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Study Notes
Introduction to Epidemiology
- The study of disease is known as pathology.
- Etiology is the study of the causes of disease.
- Pathogenesis refers to the development of a disease.
- Infection is defined as the colonization of the body by pathogens.
- Disease is an abnormal state where the body does not function normally.
Classifying Infectious Diseases
- A symptom is a change in body function that a patient feels as a result of disease.
- A sign is a change in the body that is measurable or observable due to disease.
- A syndrome is a specific group of signs and symptoms that accompany a disease.
Classifying Infectious Diseases
- A communicable disease can be spread from one host to another.
- A contagious disease is easily spread from host to host.
- A noncommunicable disease is not transmissible between hosts.
Occurrence of A Disease
- Incidence is the fraction of a population contracting a disease during a specific time, often measured as cases per year.
- Prevalence is the fraction of a population with a specific disease at a given moment, often represented as cases per 100,000 or a percentage.
- Sporadic diseases occur occasionally in a population.
Occurrence of A Disease
- An endemic disease is constantly present within a population.
- An epidemic disease appears above the normal endemic levels.
- An outbreak is the acquisition of a disease by several hosts in a specific area over a short period, often localized.
- Pandemics are worldwide occurrences of a disease.
Severity or Duration of a Disease
- An acute disease exhibits symptoms that develop rapidly.
- A chronic disease develops slowly.
- A subacute disease has symptoms that fall between acute and chronic.
- A latent disease has periods with no symptoms while the causative agent is inactive.
Extent of Host Involvement
- In a local infection pathogens are confined to a small area of the body.
- A systemic infection involves the entire body.
- A focal infection is a systemic infection that originated as a local infection.
Reservoirs of Infection
- A reservoir is a continuous source of infection.
- Humans can serve as reservoirs for diseases like AIDS and gonorrhea.
- Animals can be reservoirs for diseases such as rabies and Lyme disease.
- Nonliving reservoirs include soil, water, and can be responsible for diseases such as botulism, tetanus, and Pseudomonas.
Principles of Epidemiology
- Transmission involves the transfer of a pathogen from a reservoir to a susceptible host.
- Horizontal transmission occurs when a pathogen is passed via contact with food, water, or a living agent.
- Vertical transmission is the transfer of a pathogen from mother to fetus or child through breastfeeding.
Spread of Disease
- Direct contact occurs when one person physically touches another.
- Handwashing is a crucial measure for preventing the spread of disease via direct contact.
- Pathogens that cannot survive for extended periods are generally spread through direct contact.
Spread of Disease
- Droplet transmission involves the spread of microbes through respiratory droplets.
- Droplets generally fall within three feet of release, whereas aerosols travel farther.
- Droplet transmission is considered direct due to the close proximity required for transmission.
Spread of Disease
- Indirect contact involves transmission through inanimate objects or fomites.
- Handwashing is also a key control measure for preventing transmission through indirect contact.
Transmission of Disease
- Direct transmission requires close association between an infected and a susceptible host.
- Indirect transmission occurs through the spread via fomites.
- Droplet transmission involves the spread through airborne droplets.
Vectors
- Vectors are typically arthropods, including fleas, ticks, and mosquitoes.
- Vector-borne disease transmission occurs through two methods:
- Mechanical transmission: the vector carries the pathogen on its feet.
- Biological transmission: the pathogen reproduces within the vector.
Why are carriers important reservoirs of infection?
- Carriers may harbor infections or latent diseases without showing symptoms, making them crucial reservoirs for disease spread.
How are zoonoses transmitted to humans?
- Zoonotic diseases can be transmitted to humans via direct contact with infected animals, bites or scratches from animals, or through contaminated food or water.
Acute Infections
- Acute infections are characterized by sudden onset and a relatively short duration, with symptoms typically resolving within a few days or weeks.
Influenza Viral Kinetics
- The influenza virus exhibits a characteristic pattern of viral load over the course of an infection, starting with a rapid increase, followed by a peak, and then a gradual decline.
Interactions of Animal Viruses with Their Host
- Persistent infections involve a virus that is continually present in the host.
- Persistent infections are categorized into three types:
- Latent infections
- Chronic infections
- Slow infections
- The category is distinguished by the detectability of the virus during the period of persistence.
Interactions of Animal Viruses with Their Host: Latent Infections
- Latent infections involve a period of no symptoms after infection, followed by reactivation.
- The virus is undetectable until reactivation.
- Symptoms of reactivation may differ from the initial disease.
- Examples of latent infections include HSV1 and HSV2, and shingles (zoster).
Interactions of Animal Viruses with Their Host: Chronic Infections
- Infectious virus can be detected at all times in chronic infections.
- Disease may be present or absent during extended periods, or may develop late.
- Hepatitis B is a well-known example of a chronic infection.
Interactions of Animal Viruses with Their Host: Slow Infections
- In slow infections, the infectious agent gradually increases in amount over a long period of time.
- No significant symptoms are usually apparent initially.
- Two groups of infectious agents cause slow infections:
- Retroviruses, including HIV
- Prions, which are misfolded proteins that can cause neurodegenerative diseases like Creutzfeldt-Jakob disease (CJD).
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Description
This quiz explores the fundamental concepts of epidemiology, including the definitions of pathology, etiology, and pathogenesis. It also covers classifications of infectious diseases, their symptoms, signs, and transmission types. Test your knowledge of the occurrence and impact of diseases in a population.
