caused by invasion by a pathogen and can be transmitted from one host to another
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pathogen
infectious agent that cause disease
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host
organism infected with a pathogen
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signs and symptoms result from
damage to tissues and organs of the host
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Most common pathogen groups
Viruses (influenza, Ross River virus disease)
bacteria (tuberculosis, tetanus)
fungi (chytridiomycosis)
protists (malaria, phytophthora dieback)
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Transmission
passing of an infectious disease from an infected host to another individual
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Contagious
easily transmitted by close contact with an infected organism or their secretions (body fluids)
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Zoonotic diseases
infectious disease - transmitted from one vertebrate group to another
e.g. avian (bird) or swine (pig) influenza virus can infect humans via direct contact, close contact and indirect contact
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Ways of transmission
Direct contact with infected host’s saliva, mucus, faeces, blood or urine when handling bird or scratched
Close contact - airborne and inhaled (bird shake feathers)
Indirect contact - susceptible host comes into contact with area - infected animals live or roam - surfaces or objects contaminated
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virulence
severity of the disease it causes
\-help pathogen invade a host, cause disease + evade host defences
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susceptibility
likelihood of developing a disease;
\-if high = ability to resist disease ↓
\-depend on age, state of health, immune system
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symptoms
effects the pathogen has on the body of the host
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incubation period
time between infection and onset of symptoms
-occur due to:
pathogen dividing many times to reach numbers sufficient to cause disease
take time to reach target tissues susceptible to particular pathogen
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Disease often contagious before onset of symptoms
\-pathogen can be passed on before the person even knows they have it
\-incubation period = adaptation of the pathogen, allow it to be transmitted before host incapacitated by symptoms
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Virus
\-non-cellular pathogens = no metabolic processes
\-consists one or more strands of nucleic acid (RNA/DNA) inside protein coat (capsid)
\-microscopic = 30-300nm
\-neither prokaryotic or eukaryotic
\-obligate parasite = cannot function outside a host cell
\-limited to infecting a specific host cell or organism = virus recognise and bind to receptors on cells (adenovirus infects epithelial cell in upper respiratory tract - cold)
Studied by 0 people
