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the degree to which a pathogen can overcome the body's immune system and cause disease, capsule



Pandemic- global outbreak/worldwide spread of an infectious disease
• New pathogen suddenly appears, population has little or no immunity to the pathogen, no existing vaccines
• Spread easily (airborne particles, contact with blood or other body fluids, vectors like mosquitoes)
• Uncontrolled spread of pathogen across a wide geographic area

AIDS and Zika



Epidemic- widespread occurrence of an infectious disease in a restricted geographic area at a particular time
Sudden increase in number of cases of disease above what is normally expected in that population in that area

Ebola and Yellow fever and Swine flue


Surface proteins

Surface proteins of influenza A virus- hemagglutinin (three monomers, 19 types) and neuraminidase (four monomers, 11 types) give influenza A its antigenic properties

HA enables entry of virion into the cell where it will replicate (HA binds to sialic receptors)
Replicates using machinery of host cell and buds out of the membrane
NA enables the exit of new virus particles from a cell to infect other cells (cuts sialic receptors)

NA is an enzyme which varies in structure but active site remains constant
Relenza was developed, complementary to the shape of the active site of NA, binds to it so viruses can't infect other cells and NA stays trapped on the surface of the cell


Name of influenza

Influenza name based on its type (A,B,C), strain (host or place of origin), subtypes (differing antigenic properties, surface proteins)


Antigenic drift and shift

New subtypes that have resulted from re-assortment of their genetic material (antigenic drift)
Change in their surface proteins, different antigenic identify (antigenic shift)
Each replication can have a different nucleotide sequence or point mutation, no proofreading mechanism
Accumulation of small changes can lead to new subtypes
When one host is infected with two or more types of influenza A, new genetic material can be produced by re-assortment, mix and exchange genetic information and surface proteins
New subtypes aren't recognised by the immune system
Flu vaccinations have to be reviewed each season and updated according to new subtypes

Transferrable between species


Rational drug design

Rational drug design- process of determining enzymes produced by the infective agent and designing a drug which binds to its active site, and inhibits the processing of substrates


Antiviral drugs

Drugs are designed inhibit essential steps in the viral replication cycle in host cells
Attachment to host cell Prevent viral attachment and entry
Release of viral genes into host cell Prevent replication
Replication of viral components RNA polymerase inhibitor
Packaging of viruses Prevent assembly
Release Prevent release



Antibiotics- substance produced by a microorganism or chemical synthesis that kills or inhibits growth of microorganism
Narrow spectrum- acts against a limited variety of bacteria
Broad spectrum- act against many different kinds of bacteria
Interfere with bacterial growth and its metabolism


Identification of viruses

Identification of viruses (can't be cultured on agar plate, obligate intracellular parasite)
• Physical methods- x-ray crystallography or electron microscopy to determine structure and distinguishing features
• Immunoglobin methods (ELISA)- blood sample containing antibodies taken and added to a specific antigen of a virus, if complementary they bind together, unbound material is washed away, second antibody with an enzyme indicator and its substrate added, solution changes colour if the second antibody was able to bind to the antigen
• Molecular techniques- locate specific DNA sequences, reverse transcription of proteins to identify RNA virus


Identification of bacteria

Identification of bacteria (correct antibacterial treatment)
• Physical methods- microscopy to differentiate bacteria based on shape, size, capsule and gram-stain, different media to observe growth patterns (facultative/obligate)
• Immunological methods-