Key Knowledge 9 Flashcards
infectious disease
an illness caused by a pathogen that can be transmitted between individuals
pathogen
an agent that causes disease
re-emerging disease
an infectious disease that was previously under control but that is now increasing in incidence
emerging disease
an infectious disease that is new to the human population, or that is rapidly increasing in incidence
Evolution of causative organism
The pathogens causing disease can evolve to either infect humans or, if previously capable of infecting humans, evolve to evade treatments by acquiring resistance.
Globalisation and travel
Due to our ability to quickly travel around the world, diseases that would otherwise have remained localised to a specific area can quickly spread to multiple countries
Increased exposure of humans to animals
As the human population grows and climate change alters the environment, humans are more likely to come into contact with animals. A zoonosis is a disease caused by a pathogen that has been transmitted to humans from another species.
Increasing human population
Larger populations lead to increased population densities in cities, increasing the likelihood of a disease spreading and causing large scale health problems for a population.
Changing technology
Sometimes new technology can be responsible for the emergence or re-emergence of a disease. For example, Legionnaires’ disease is caused by a pathogen that inhabits air conditioning systems.
Insufficient vaccination of the population
Previously managed diseases can re-emerge if the proportion of a population that is vaccinated against the disease decreases. This stems from the loss of herd immunity, with an increase in the number of susceptible individuals allowing the pathogen to more easily spread between individuals.
epidemic
a dramatically increased occurrence of a disease
in a particular community at a particular time
pandemic
an epidemic that has spread across multiple countries and/or continents
Physical method of identifying pathogens
Visualising pathogens using microscopes to determine their structure
Phenotypic method of identifying pathogens
Selective media – an agar plate designed to allow certain pathogens to grow and multiply to test for their presence in a sample
Biochemical test panels – a series of tests designed to specify a sample’s genus and species.
Immunological method of identifying pathogens
Serology – the diagnosis of disease based on the presence of antibodies or antigens in a person’s serum. One example used to detect the presence of pathogenic antigens in a sample is the enzyme-linked immunosorbent assay (ELISA). There are four main
types of ELISA tests – direct, indirect, sandwich, and competitive.
Molecular method of identifying pathogens
Hybridisation-based detection – labelled segments of genetic material that are complementary to a pathogen’s genetic material are added to a sample. If a signal is generated, it means a pathogen is present.
Whole-genome sequencing – provides detailed information about the pathogen.
Airborne transmission
Pathogens spread via very small particles that stay in the air for prolonged periods of time
