Community infections and their control

What are the ways infections can be transmitted?

non-human source to humans, person to person either directly or indirectly

Examples of infections coming from person-person indirect contact

mosquitos causing malaria, surfaces spreading colds, and sharing needles for HIV.

What are the consequences of transmission?

Endemic disease, outbreak, epidemic, pandemic

Define endemic disease

usual background rate

define outbreak

two or more cases linked in time and place

define epidemic

a rate of infection greater than the usual background rate

define pandemic

Very high rate of infection spreading across many regions, countries, continents

define Ro (reproduction) number

the average number of cases one case generates over the course of its infectious period, in an otherwise uninfected, non-immune population

What does it mean if Ro is less than 1?

decrease in cases

What does it mean if Ro is more than one?

Increase in cases

What does it mean if Ro is 1?

stable number of cases indicating a steady state of infection transmission.

What is the reason for outbreaks, epidemics and pandemics?

new pathogen (antigens, virulence factors, antibacterial resistance), new hosts (non-immunes, healthcare effects), new practices (social, healthcare)

What factors determine transmissibility?

The infectious dose varies by the specific microorganism, how the microorganism is presented and the immunity of the potential host

Define infectious dose

number of microorganisms required to cause infection.

Give examples for potential infection interventions that target pathogens and vectors

Reduce/eradicate pathogen (antibacterials including disinfectants, decontamination, sterilisation), reduce/eradicate vector (eliminate vector breeding sites)

Give examples for potential infection interventions that target patients

improving health (through nutrition and medical treatment), building immunity (passive immunity through maternal antibody and intravenous immunoglobulin and active immunity through vaccination)

Give examples for potential infection interventions that target practice

avoidance of pathogen or its vector (PPE and avoiding geographic locations), behavioural (safe sex, safe disposal of sharps, food and drink prep)

Give examples for potential infection interventions that target place

environmental engineering (safe water, safe air, good quality housing, well designed healthcare facilities)

What does infection prevention and control require?

multi-disciplinary skills ranging from molecular biology to political advocacy, “from genes to latrines”

Define herd immunity.

resistance to the spread of an infectious disease within a population that is based on pre-existing immunity of a high proportion of individuals as a result of previous infection or vaccination.