PATH 3610 Lecture Notes - Lecture 15: Atypical Pneumonia, Microcephaly, Rotavirus
14 May 2018
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INFECTIOUS DISEASE
Infectious diseases
- Infection: multiplication of a parasitic organism in or on a body
Rotavirus infection of children:
- Rotavirus is vomiting and diarrhea
o or vomiting only or diarrhea only
- All children infected in first 4 years
o Incidence – 25% per year
o Prevalence at 4 years – 100%
- Infectious and contagious
- USA
o 2000,000 hospitalisations/year
o 500 deaths/year
- Asia, Africa, Latin America
o 5 billion cases per year
o 10 million deaths per year
Zikavirus
- arbovirus – mosquito
- viremia and systemic inflammation response
- transplacental (vertical transmission: parents (mother) to offspring) →
crosses placenta
- microencephaly → encepho = brain
Infectious agents
- prion, viruses, chlamydia (STI), rickettsia (spread like ticks), mycoplasma
(form of pneumonia – walking pneumonia), bacteria (germs), fungi, protozoa,
helminths, arthropods (ticks, lice)
Prion
infectious protein
Viruses
Obligate intracellular
20-30 nm
Chlamydiae
Obligate intracellular
200-1000 nm
Ricketsiae
Obligate intracellular
300-1200 nm
Mycoplasma
Extracellular
125-350 nm
Bacteria
Intra and extracellular
0.5-15 um
Fungi
Intra and extracellular
Protozoa
Intra and extracellular
Helminths
Intra and extracellular
Arthropods
extracellular
-
Some principles
- politics play a major role in definitions
- endemic (native)
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- epidemic (many people)
- pandemic (all of the people)
- if there is a high mortality disease, that disease is new – no coexistence?
o (asnt been in people for a long time
o Ex. Ebola virus, HIV (initially)
- Endo = within, epi = above, pan = all
- Individual variation:
o There is a different response to infectious agents in all people
o People are similar enough that we call norm
o (%% of people are within 2 SD above and below mean
- Risk
o Real risk is statistical
o Perceived risk leads to mass psychosis
Spread of infectious disease
- direct or indirect (vector)
o Indirect
▪ vector is insect or other organism
o direct transmission
▪ vertical → from mother before or at birth
▪ horizontal → from one to another after birth
▪ some are contagious – transmitted directly to another host of
same species
- Aerosol:
- Contact: very common
- Feco-oral: 70%-80% of feces is bacteria
o Ex. dogs eat cat and horse feces
- Nosocomial: hospital or care
- Vertical vs. horizontal
- Zoonotic: animal disease spread to humans, usually vertebrate → from
vertebrate animal source
Human intervention in disease
- prevention of disease: individual, population
- control of disease: population
- treatment of disease: individual
Prevention of disease
1. Avoid contact (and sanitation)
a. Inherent
b. Enforced/isolation/quarantine
i. Isolation – separates sick individuals from well individuals
ii. Quarantine - separates people exposed to a disease (ex. when
in contact with someone with a disease but not yet showing
signs)
c. Eradicate
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