Virology Flashcards
What are the three requirements for classification as a virus?
- Sub-microscopic entity
- Single nucleic acid surrounded by a protein coat
- Obligate intracellular parasite
What are the 6 stages in virus life cycle?
Attachment, entry, replication and protein synthesis, assembly and release
Define viral pathogenicity
The severity of disease caused by different viruses
Define viral virulence
The severity of disease caused by different strains of the same virus
5 types of viral replication (ie single strand RNA, double strand DNA etc)
- Single strand RNA positive sense-the viral RNA can be used directly to make protein
- Single strand RNA negative sense-the viral RNA must be transcribed to positive sense (complimentary base pairing) and then is used to make protein
- Double stranded DNA-same as human replication but using viral enzymes (important in antivirals)
- Double stranded RNA-only example is rotavirus
- Retrovirus-genome is transcribed to double stranded DNA using reverse transcriptase then integrated into the host genome using integrase
What is the stage of the viral life cycle most commonly targeted by antivirals?
Replication
Define incubation period
The time between becoming infected with virus and symptom onset
Define generation time
The time between virus exposure and becoming infected to others
Define reproductive number
The number of subsequent infections in a susceptible population that can be caused by a viral illness in 1 individual during the infective period
What are the 5 patterns of viral illness?
Acute, subclinical, persistent and chronic, latent (acute and then persistent latent) and slowly progressive (the disease takes years to manifest)
What are the two types of rash and the relevance of them in diagnosis?
Maculopapular rash-the rash is caused by the immune response to the virus rather than the virus itself so cannot be used in diagnosis
Vesicular rash-can diagnose from the rash alone based on location, stage etc
What nucleic acid are measles, mumps and rubella? How are they transmitted?
All are single stranded RNA viruses (measles and mumps are negative sense and rubella is positive sense)
Respiratory transmission
What is the prodrome of measles?
What else will you see in an infected individual?
The 3C’s-conjunctivitis, cough and coryza.
Koplik spots, person will be very unwell(fever, malaise and anorexia)
What is the incubation period of measles?
What is the infectious period?
Incubation period-10 to 14 days
Infectious period-2 days before the rash until 10 days after
Complications of Measles infection
Secondary bacterial infection, encephalitis (10 days after) and sub-acute sclerosing encephalitis (6-8years after infection)
What are the risk groups in measles infection?
Immunocompromised, pregnancy and neonates
What is the incubation period of rubella?
What is the infectious period?
IP-14 to 21 days
Infectious 7 days before the rash until 7 days after
What are the complications of rubella?
Congenital rubella syndrome!-before 12 weeks risks serious malformation (so termination is offered) and 13-16weeks risks sensorineural hearing loss
arthralgia
What are the other names for Parvovirus B19?
Slapped cheek disease, fifth disease, erythema infectiosum
What is the incubation period for Parvovirus B19?
What is the infectious period?
IP-14 to 21 days
Infectious 7 days before the rash until the day the rash appears (so infection control is impossible)
What type of virus is Parvovirus B19?
Single stranded DNA
What does Parvovirus B19 infect, in that case who is at risk in infection?
Infects RBC progenitors, therefore risk in haemolytic disorders where it can precipitate an aplastic crisis
Risk groups in Parvovirus B19 infection
Haemolytic disorders-aplastic crisis
Immunocompromised
Pregnancy-if infection at less than 20weeks hydrops foetalis
What are the complications of HHV6 and HHV7?
Encephalitis and in transplant
