HLTB21H3 Lecture Notes - Lecture 8: Multiple Drug Resistance, Shigella Dysenteriae, Foodborne Illness

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25 Nov 2013

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November 7, 2013- Lecture 8
Many of the diseases have been around, but haven’t diagnosed them in humans-
they’ve existed in animals mostly
The Third Epidemiological Transition
Persistence of Chronic Non-Infectious Diseases,
Newly Emergent & Re-Emergent Infectious Disease
Infectious diseases notable for
1) many new diseases causing mortality being detected;
2) increased incidence and prevalence of previously controlled (re-emergent)
infectious diseases;
3) many re-emergent pathogens evolving into drug-resistant strains
The interaction of:
1) Socialchange
2) Demographicchange
3) Environmentalchange
4) Microbialadaptation
5) Medicalmalpractice
CDC: Emerging infectious diseases are those infections that appeared recently in a
population, or those that already existed but are spreading rapidly, in terms of both
incidence and geographical distribution
(Grisotti and Avila-Pires 2010)
Institute of Medicine (IOM), 1992: “new, re-emerging or drug-resistant infections
whose incidence has increased in the last two decades, or whose incidence
threatens to increase” (Cohen 2000)
Third transition: very fluid
Issue of shift from second transition
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Second transition starts turn of the century
Post WW2
Important factor in decreasing infectious disease
Burden of disease:
In terms of persistence of infectious disease: we have to attribute HIV/AIDS as a
significance factor -> it affects millions of people -> diminishes immune system
Immuno-compromised bodies: our immune system has changed
We are aging population: we’re living longer. -> hence we have inseparable chronic
diseases; in the past we didn’t live long enough to suffer from those kinds of disease,
like heart failure, etc.
It can be emergent in one location and be somewhere else in another location
Issues in recognition.
1. Recent introduction of a new etiological agent (or its recognition)
2. Mutation arising in an existing agent
Followed by its rapid dissemination in the population
Grmek (1993) substituted the idea of emergence for that of novelty and
proposed five distinct historical instances for the recognition of emergence
and novelty.
1. It existed before being recognized, but escaped medical attention because it went
unrecognized as a nosological entity of its own.
2. It existed, but was only detected after a qualitative and quantitative alteration of
its characteristics made it noticeable (pathogen evolution).
3. It was introduced in a region where it did not occur previously, i.e., due to war,
migration, population movements
4. The emergence of a disease acquired from a non-human reservoir (zoonoses).
5. A new disease emerges and spreads, when the causal agent or the necessary
environmental conditions for its occurrence did not exist before the first
clinical observations identified its presence; also possibly as a result of
laboratory manipulation of pathogenic organisms intended for research,
biological warfare, or genetic engineering of agricultural products
(Grisotti and Avila-Pires 2010)
6. In addition to the categories proposed by the CDC and by Grmek, Grisotti and
Avila-Pires (2010) add the role of under-notification of those conditions presented
by official lists of diseases subjected to compulsory notification, and also the failure
to recognize and notify uncommon diseases.
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“Under-notification is at the basis of many emergent diseases. These cases occur and
are diagnosed, but doctors and health authorities ignore or fail to report them.”
3. 16th century: considered newly emerging, but they were actually brought there.
4. First restricted to animals, but not affecting humans
5. new form of anthrax
6. New emerging meaning newly recognized by medical professionals
Newly emergent disease: Crutezfeld Jakob Disease (human form of Mad Cow)
Today we can’t think of infectious and chronic disease. A lot of the infectious
ones might lead to chronic.
Bacterial infections can lead to ulcers.
Confusion with syphilis:: confused with leprosy.
so when it appeared, confused with a new disease.
Newly emerging diseases:
Toxic Shock Syndrome: first clinically recognized in 70s and 80s- bacterial infection
infecting women, those who used tampons, because it led to blood infections and led
to shock, hence they died.
MRSA: streptococcus orios -> this form is anti-biotic resistance. It’s new in the sense
because we haven’t had this type of infection prior to 10-15 years.
Food-Borne Disease
Food safety can be compromised at many levels today, esp. due to massive
scale of food production - especially animals (though note, beginning of 20th
century was more challenging due to various factors...)
Emergence of non-typhoid salmonellosis, campylo bacteriosis, listeriosis, and
infections involving E. coli O157:H7, Cyclospora, calicivirus and Vibrio vulnificus
Estimated that food-borne illness accounts for 76 million illnesses, 325,000
periods in hospital and 5,000 deaths in the United States annually (Mead et al. 1999)
Sterosis related to food products.
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