26 - transmission of viral disease Flashcards
cycle of transmission of viral disease
- transmission
- entry
- primary site replication
- spread within host
- shedding
- transmission
controlling virus infection depends upon breaking this cycle
3 modes of virus transmission
horizontal transmission
• person to person
vertical transmission
• mother to baby
zoonosis
• animal to man
most common type of viral horizontal transmission
respiratory and faecal-oral transmission
types of viral horizontal transmission
- respiratory
- faecal-oral
- sexual
- urine
- mechanical
respiratory viral transmission
droplets may: • be directly inhaled • infect conjunctiva • fall onto surfaces • be dessicated (inactivated)
droplet size is important in determining route of transmission
faecal-oral viral transmission
very effective mode of transmission - viruses grow to high titres
examples:
• rotavirus
• hepatitis A
• polio virus
sexual viral transmission
few viruses are spread by this
but those that are pose a serious health risk
examples: • HIV-1/AIDS • hepatitis B virus (HBV) • human papilloma virus (HPV) • herpes simplex virus (HSV)
urine viral transmission
rare
glomerular nephron filters blood and viruses too big to pass through the filter
mechanical viral transmission
blood borne viruses can be transmitted by any activity which involves transfer of blood from 1 person to another
e.g. • drug abuse • blood transfusion • tattooing • body piercing • surgery
examples
• HIV
• hepatitis B and C
viral vertical transmission
can be a primary infection of mother while pregnant or reactivation of a persistent infection
transplacental - rubella
during birth - herpes simplex
post natal - HIV, hepatitis B
zoonosis
animal to man transmission
animal in which the virus replicates is known as the reservoir (or primary host)
animal which transmits the virus is known as the vector
factors affecting viral transmission
- sanitation
- climate
- viral vectors
- healthcare
- population density
- behaviour
- poverty
6 steps of virus multiplication
- attachment
- penetration
- uncoating
- biosynthesis
- assembly
- release
what does viral entry into a host cell depend on?
the interaction between the viral surface protein and the host cell surface protein (virus receptor)
what is biosynthesis?
genome replication + mRNA synthesis + translation
