Epidemiology of Infectious Diseases Flashcards
Parasitism
A type of symbiotic association between 2 species where one benefits (the parasite) ny exploiting the resources of the other (the host)
Endoparasites
Complete some or all of life cycle within host tissues or cells
What are two subtypes of endoparasites?
Microparasites (pathogens) and macroparasites
Three major taxas of microscopic endoparasites
Viruses, bacteria, and protozoa
(minor ones: fungi and prions)
Macroparasites are different from microparasites because they complete ____ of their life cycle within the host.
Part
(usually release infective stages from the host)
Ectoparaties
Live on surface of host
ex. Ticks, mites, fleas, mosquitoes, leeches, etc.
Direct transmission
Physical or close contact between hosts which allows disease agent to transfer from an infected host to an uninfected one
Indirect transmission
Transfer of a disease agent from an infected host to an uninfected one facilitated by an intermediate host or a vector
Ecological categories of infectious disease
Zoonotic
Multi-host
Human-specific
Zoonotic diseases are defined as…
Diseases transmitted from animals to humans only
ex. Lyme disease, Hanta virus
Multi-host diseases are defined as…
Diseases that transmit between both animals and humans
ex. Influenza virus
Human-specific diseases are categorized as…
Diseases transmitted from human to human
ex. Measles, HIV – but most have zoonotic/multi-host origins
Schistosomiasis, also called the ____ ____ ____ ____, is caused by aquatic trematodes that use ____ as intermediate hosts.
Plague of the Pharaohs; snails
Why was schistosomiasis prevalent in Eygpt?
The Egyptian civilization had great success with irrigation and controlled flooding of the Nile, but it also created conditions favorable for Schistosomiasis – Lots of water year-round ensured land productivity, but also led to greater possibility to parasite exposure.
The impoundment of water causes ____ ____ ____, which leads to ____ ____, and attracts ____, the intermediate host of schistosomiasis.
Accumulation of nutrients; Algal bloom; Snails
The Plague was caused by the ____ that was transmitted by ____ that were carried by ____, the anthropophilic ____ ____.
Bacteria; Fleas; Rodents; reservoir hosts
Bubonic Plague
Infests lymph system, causing lymph nodes to undergo hemorrhagic inflammation
Septicemic Plague
Causes disseminated intravascular coagulation within the bloodstream, preventing subsequent clotting as clotting factors and platelets are used up
Pneumonic Plague
Infests lungs, typically following bubonic/septicemic syndrome
*Human specific
Justinian plague (541-542 AD and a second wave in 588) killed over ____ ____, which contributed to the fall of the classical world and beginning of the ____ ____.
100 million; Dark Ages
Black Death (1347 - 1351) Killed ____ ____ (~1/4 world population) and is considered the most severe pandemic in human history
1500 million
Third Pandemic in Asia (1855 - 1900) likely had two different forms of transmission (____ and ____)
Bubonic; pneumonic
Medical advances motivated by smallpox epidemics
- Inoculation: Intentional infection with a minor strain of smallpox virus, which conferred protection against the more virulent or major strain (could still kill ppl)
- Vaccination: Used a vaccine derived from the vaccinia virus in the 19th century
Characteristics of Type I Epidemic
- Occur in large populations
- Regular peaks
- Never disappears
*Example: Flu
Characteristics of Type II Epidemic
- Occur in smaller populations
- Discontinuous peaks
- Periods of temporary absence of disease
*Example: Mumps
Characteristics of Type III Epidemic
- Occur in very small populations
- Highly irregular outbreak intervals
- Extended absence of disease
*Example: Ebola
Pandemics
Epidemics that spread globally, tend to be driven by novel strains of highly infectious pathogens
Most pandemics originate from one or more ____ events, where…
Spillover; A novel pathogen enters into a new host population
The 1918 Pandemic Flu (Spanish Flu) was caused by
H1N1 strain
The 1918 Pandemic Flu (Spanish Flu) was likely exacerbated by…
- Troops kept in close quarters & poor health
- Massive global movement of humans
We define Emerging Infectious Diseases as the diseases that are increasing in…
- Incidence (rate of human cases)
- Pathogenicity (how virulence it is)
- Geographic range (spacial distribution)
- Host range (number of species infected/affected)
- Societal impact (possibly due to an interaction with changing social factors)
1st pandemic of the 21st century
SARS
- 10% fatality rate
- Originated in SE China
- Caused by SARS-CoV
- Horseshoe bats were found to contain high prevalence of antibodies to it, but the genetic structure of SARS in bats does not interact with human cells
- Still a missing link
2nd pandemic of the 21st century
Swine-origin H1N1
- Started in Mexico, caused high death rates in healthy adults
- Strain = reassortment of gene segments from 4 other H1N1 strains
- Likely jumped from pigs to humans
Factors that will have the greatest impact on your risk of exposure to infectious diseases in the 21st century
- Globalization
- Ecosystem
- Wildlife Trade
- Antimicrobial resistance
How would globalization affect disease transmission?
People are moving a lot further and a lot frequent, and more efficient than ever before, so does the pathogens.
How would ecosystem change affect disease transmission?
The growth and development of human population is profoundly altering the biological complexity of the Earth. The exploitation of ecosystems can cause a decrease in reservoir hosts of certain pathogens, and more human-wildlife interactions, which promote pathogen transmission.
ZIKV was detected due to a surge in infant _____, and was first detected in Brazil in the Americas
Microcephaly
ZIKV in the Americas were introduced by a ____ event and was ____ than previously considered, but was consistent with an increase in trael from ZIKV areas during the Confederations Cup
Single; Earlier
Why isn’t MERS considered a pandemic?
It didn’t spread to affect enough population to be recognized as one
Three hypothesis for the emergense of COVID-19
- Zoonotic Emergence: Spillover event from bats to humans either directly or indirectly
- Lab Leak: Researcher studying SARS-CoV-2 (or its immediate progenitor) accidentally became infected and spread the infection beyond the lab
- Genetic Engineering:Intentionally created in a lab setting and then accidentally or intentionally released to the public
Why is tuberculosis reemerging?
Antimicrobial resistance
2 types of antimicrobial resistant strains of tuberculosis
Multi-drug-resistance TB (MTB) and Extensively drug-resistance TB (XTB)
MTB is resistant to the ____ main antibiotics (____ of new cases), whereas XTB is resistant to ____ or more of the 6 second-line therapies (____ of new cases)
2; 20%; 3; 2%
What is Jaccard’s index used for?
It is a continental scale to estimae the similarity in species composition between two communities
- Identical communities: J = 1
- Completely dissimilar communities: J = 0
