Containment - lecture 3 - control of infectious disease

one health

• human, animal and environmental

  

infection

• when a microorganism is present in a host in placed where it is not normally found (replicating)

infectious disease

• when the microorganism causes symptoms

different things that cause disease

• bacteria

  • cholera, TB, e. coli 

• viruses

  • HIV, HPV, hepatitis

• protozoa

  • malaria, giardia

• multicellular 

  • helminths, fungi, algae 

• external organisms 

  • fleas

• nonliving 

  • prions (mad cow disease) 

direct versus indirect transmission

• Direct: skin skin, blood, across placenta, sneeze cough, breast milk

• Indirect: food, water, vector borne

subclinical

• don’t have symptoms (yet)

• don’t see them as they don’t get sick  but carry the disease

index case

• the first case identified in the population

primary case

• case that brings infection into a population

reproductive rate

• how many people one person can infect

explain this type of epidemic curve

• All cases are exposed to the same source at about the same time (a single exposure event).

• The number of cases rises rapidly, peaks, and then falls gradually — forming a sharp, single peak.

• Transmission: No person-to-person spread

• Example: Food poisoning from a contaminated meal at a wedding — everyone exposed at once.

explain this type of epidemic curve

• Exposure to the source occurs over a prolonged period (days, weeks, or longer).

• As long as exposure continues, new cases appear.

• The curve shows a plateau or broad peak rather than a sharp one

• Transmission: Still from the source — not person-to-person

• Example: Typhoid fever from a continuously contaminated water source.

explain this type of epidemic curve

• propagated outbreak 

• Caused by person-to-person transmission (propagation).

• The curve shows successive waves, each separated roughly by one incubation period.

• The first case is the index case, and secondary, tertiary waves follow.

• Transmission: Person-to-person spread

• Example: Measles, influenza, or COVID-19 spreading within a community.

epidemiological triangle

• public health model that explains disease transmission by examining the relationship between three key components

  • the agent 

  • the host 

  • environment 

adequate chain of transmission

• 

  reservoir of disease very important

• Types of host – humans are intermediate host of malaria!

limiting infectious disease, control, elimination, eradication

• control → reduction of disease incidence, prevalence, mortality and morbidity

• elimination → reduction to zero of the incidence of infections caused by a specific agent

• eradication → permanent reduction of the incidence of infections worldwide 

what does disease control aim to do

• reduce incidence of disease

• reduce duration of disease → and thus risk of transmission 

• reduce effects of infection 

• reduce financial burden 

control strategies (jenkins) 

• problem definition

• proposal development and assessment of success  of implementation economic assessment

• societal relevance

• policy development

• professional and public acceptance

• political decision

public health surveillance definition and goal

• definition → the systemic collection, analysis and interpretation of health data on an ongoing basis and its timely distribution to those who need to know and subsequent use of the data 

• goal → to prevent or control the diseases within a population by knowing and timely action. 

passive surveillance

• using existing routine structures to inform about infectious diseases (Stronger health system= more coverage with passive surveillance)

• it is based on the data being readily available and the health care providor providing this data. 

advantages and disadvantages of passive surveillance

• advantage; 

  • inexpensive

  • covers many diseases

  • allows for international comparisons

• disadvantage

  • depended on many actors

  • limited access to health facilities

  • under-recognition of diseases (non specific symptoms)

active surveillance 

• based on periodic field visits to identify new cases 

• more expensive, difficult to develop but accurate reporting and local outbreaks are identified

advantages and disadvantages of active surveillance

• advantages

  • reporting is more accurate

  • local outbreaks are generally identified

• limitations

  • more difficult to develop for routine work

  • more expensive to maintain

  • potentially invasive of privacy

dutch public health act 

• contains list of notifiable diseases 

• contains measures (MHS/GGD) may take to control infectious disease 

• mayor is responsible for control actions → force measures upon patients 

• A1&2 → isolation of patient, examination, observation quarantine of contacts

  • A1 → potential pandemic threat 

  • A2 → immediate reporting after suspected case 

    • small pox, poliomyelitis, SARS, MERS, viral hemorrhagic fever (EBOLA) 

• B1 → all measures except quarantine of contacts

• B2 → only exclusion from workplace 

• C → only advice no measures enforcable on patient 

levels of prevention

primary prevention

• action taken prior to the onset of disease, which removes the possibility that the disease will ever occur. 

• health promotion (talking) and specific protection (eg immunization)

  • health promotion → the process of enabling people to increase control over the determinants of health and thereby improve their health

• medical primary prevention

  • vaccination of risk groups 

  • use of prophylactic medicines 

  • MDA

expanded programme on immunization (EPI)

• routine vaccinations. “cold chain problem” issues in low/middle income countries – temperature of fridges as vaccines need to be cold

MDA

• issues with releasing into nature, resistance – have to be very careful

difference isolation and quarantine 

• isolation → seperation and restricted movement of ill people with contagious diseases. primarily on individual level

• quarantine → restriction for well people, still in use for highly contagious infectious diseases (EBOLA)

secondary prevention

• preventative screening 

• rapid tests to identify things quicker and treat quicker = prevent transmission

tertiary prevention

• prevention of increasing disability and death 

• ART to prevent transmission of hiv