Public Health Module 3 Exam

infectious disease

~25% of worldwide deaths

result from the infection, presence, and growth of biological agents in a host organism

aka communicable, contagious, or transmissible diseases

underprivileged, elderly, children, and debilitated

who are particularly affected by infectious disease?

communicable pathogens

transmitted from host-to-host (cannot live outside a host)

non-communicable pathogens

live in an abiotic environment

contagious pathogens

easily transmitted

modes of transmission

contact with environmental sources

animals: zoonosis or intermediate host

person-to-person contact

pathogen biology, environmental, host factors, and societal

transmission and infectivity

pathogen biology

reproduction

survival outside of host

adaptations for infectivity

environmental

housing

sanitation

water quality

climate

host factors

susceptibility

immunity

lifestyle/behavior (exposure)

societal

healthcare access

public health infrastructure

globalization

R-naught

in epidemiology, basic reproduction number (or ratio)

expected number of cases directly caused by another case

• generated from mathematical modeling

• assumes entire population is susceptible

• R effective (Re)=R0*fraction susceptible

R0>1

cases increasing

R0=1

cases stable

R0<1

cases decreasing

endemic

constant level in a community (baseline)

outbreak

increase in limited area (ex. school, city…)

epidemic

sudden increase in large area (ex. country)

pandemic

epidemics in multiple countries (ex. world)

block transmission, vaccines, and diagnosis and treatment

three major strategies to control and prevent infectious disease

hand hygiene

what is one of the most effective interventions against infectious disease?

cost effective

respiratory infections and diarrheal diseases are ~half of all infectious disease deaths

especially important for healthcare-associated infections (HAI)

pathogenicity

ability to cause disease (genetic component)

virulence

relative capacity to cause disease (degree of pathology)

usually correlates with ability to replicate within host

various degrees of this may be exhibited depending on conditions

the more virulent, ___ chance for transmissions

less

the less virulent, ____ chance for transmission

more

respiratory infections, AIDS, and diarrhea

the Big Three of leading causes of death by infectious disease

cold

caused by >200 viruses

less virulent and limited to upper respiratory tract

flu

caused by influenza virus

more virulent and can infect lower respiratory tract

can start with cold-like manifestations and worsen

often 1-2 week recovery

infectiousness, environment, exposure, and susceptibility

transmission factors

infectiousness

number of infectious pathogen particles expelled

environment

small and enclosed spaces favor transmission

exposure

duration, frequency, and physical proximity

ex. daily contact with family, friends, classroom, co-workers

susceptibility

immune status (including vaccination) of exposed individual

viral vaccines

MMR (measles, rumps, rubella)

chickenpox

respiratory syncytial virus (RSV)

influenza

cold

bacterial vaccines

DTaP (pertussis/whooping cough, Diphtheria)

haemophilus type B/meningitis

pneumococcal pneumonia

flu vaccine

strains reviewed annually

-strains circulating at end of previous flu season used to make vaccine

-recommended to be vaccinated annually

-efficacy varies

especially recommended for high-risk individuals (elderly or compromised)

-protects against severe disease and promotes quicker recovery

tuberculosis (TB)

caused primarily by Mycobacterium tuberculosis

very common infection

-estimated 1.7 billion people infected

-millions of death per year

primarily affects the lungs

-transmitted via droplet-nuclei (aerosol)

-can spread to other organs and tissues

infection can be active (symptoms) or latent (asymptomatic)

features of tuberculosis

mycobacterium grows slowly

immune system cannot completely eliminate

causes a lifelong chronic infection

latent (LTBI)→active

pathology due to inflammation

most cases are curable

control and prevention of TB

relies heavily on early diagnosis and treatment

typical treatment protocol: isoniazid, rifampicin, pyrazinamide, and ethambutol for 2 months

INH or RIF for 4-9 months for LTBI

compliance is problematic

directly observed therapy, short course (DOTS)

a reliable person observes patient swallowing the tablets

-health care worker

-family member

prevents relapse and spread of TB

slows development of drug resistance

_____depend on region of respiratory tract that is affected

clinical manifestations

upper respiratory tract

>transmission

<virulence

lower respiratory tract

<transmission

>virulence

aerosols, respiratory droplets, or hands

common modes of transmission

lower respiratory tract infections are more _____

severe

examples of lower respiratory tract infections

influenza, COVID, bacterial pneumonia, TB

________is major problem with tuberculosis

drug resistance

multidrug resistant (MDR) TB

resistance to INH and RIF and others

requires treatment with second-line drugs

higher mortality rate (lower cure rate)