Patterns of viral infection Flashcards
What is iatrogenic transmission?
Health care worker responsible (e.g. contaminated needles)
What is nosocomial transmission?
Acquired in hospital
What is vertical transmission?
From parent to offspring
What is horizontal transmission?
From one person to another
What is germ line?
Part of the host genome (e.g. integrated retrovirus)
Name some virus routes of entry to the body
- Skin
- Mucosal surfaces (respiratory, enteric, genital tract)
- Conjunctiva
- Blood
- Bites
What are arboviruses?
Viruses spread by insects
What is viraemia?
Virus in the blood
Describe the dissemination of viruses from the site of entry.
- Primary viraemia (spread of virus in the blood)
- Amplification (replicate in a certain organ)
- Secondary viraemia
- Target organ
TRUE OR FALSE:
In local infection, the virus goes in and out of the basal surface of cells
FALSE
Local infection = apical release
TRUE OR FALSE:
In dissemination, the virus goes in and out of the basal surface of cells
TRUE
Dissemination = basal release
What is the difference between a local infection and a systemic infection?
LOCAL = virus does not spread
SYSTEMIC = virus affects the whole body (i.e. an infection in the bloodstream)
What is meant by the term “haematogenous spread”?
Virus spread through the blood
What is meant by the term “neural spread”?
The virus is spread into the nervous system
TRUE OR FALSE:
A viral rash is indicative of a local infection
FALSE
It indicates a systemic viral infection - virus leaves blood and enters skin = cells destroyed by virus replication
What is tropism?
The predilection of viruses to infect certain tissues and not others
What 3 factors is tropism defined by?
- Receptor interactions (susceptibility)
- Ability to use the host cell to complete replication (permissivity)
- Whether the virus can reach a tissue (accessibility)
Describe the tropism of HIV
Viral attachment protein GP120 on HIV binds with CD4 and CCR5 or CXCR4 co-receptors on T-cells
What is pathogenicity?
The ability of the virus to cause disease
What is virulence?
The capacity of a virus to cause disease.
This depends on how much replication the virus undergoes and is affected by other factors (e.g. host response)
What are the different viral infection outcomes?
- Acute infection (followed by viral clearance)
- Sometimes ‘accidental’ tissue infected with permanent damage despite viral clearance
- Persistent infection
- Latent reactivating
- Slow
- Oncogenesis
Name 3 viruses that causes acute infection
- Variola virus (smallpox)
- Influenza virus
- Poliovirus
- Rubella virus
Name 3 viruses that causes persistent infection
- Varicella-zoster virus
- Measles virus
- HIV-1
Name a virus that causes latent reactivating infection
- Herpes simplex virus
Name a virus that causes slow infection
- Measles virus SSPE
- Human immunodeficiency virus
- Human T-lymphotropic virus
Name oncogenic viruses and the types of cancer that they cause
- HHV8 –> Kaposi sarcoma
- HTLV-1 –> adult leukaemia
- HPV –> cervical cancer
- Hepatitis B and C –> hepatocellular carcinoma
- Epstein Barr –> Burkitts lymphoma, Hodgkins lymphoma and nasopharyngeal carcinoma
What factors determine the outcome of virus infection?
Balance between virus virulence and host response:
- Virus sequence
- Virus load
- Host immune response/status
- Host co-morbidity
- Co-infections
- Other medications
- Host genetics
- Host age and sex
Give an example of viral load affecting the outcome of an infection
The first child in the family to contract chicken pox often has a milder illness than the second child.
This may be because the second child is in closer contact and became infected by a higher dose
