morphology and biology of viruses

Question 1

criteria for virus classification

Answer 1

• type and organisation of the virus (RNA/DNA? single/double stranded? genome relatedness?)
• how does the virus replicate (e.g. reverse transcriptase?)
• structure/size of replicate
• range of hosts

Question 2

characteristics of herpes herpidae

Answer 2

have an icosahedral nucleoplasmid. dsDNA that is linear. are enveloped and posses the ability to lay latent and then reactivate

Question 3

characteristics of HIV

Answer 3

enveloped RNA virus. contains reverse transcriptase. two viral surface proteins = gp120 and gp41 involved in infecting Th cells

Question 4

characteristics of Hepatitis A virus

Answer 4

naked RNA virus (not enveloped) icosehedral in shape. is +ve sense (= viral RNA can be directly translated, no need for transcription)

Question 5

characteristics of hepatitis A virus infection

Answer 5

incubates for 15-45 days. is an acute onset. more common children and young adults. transmission mainly faeco-oral. can be sexual. unlikely percutaneous or perinatal

Question 6

characteristics of hepatitis B virus

Answer 6

is enveloped DNA virus. Partially double stranded. icosahedral in shape. can exist as complete virus or incomplete particles of tubular filaments of virus surface antigen.
virus found in bodily fluids

Question 7

characteristics of hepatitis B virus infection

Answer 7

incubates for 30-50 days. is acute or insidious onset. more common in young adults, babies, toddlers. percutaneous transmission, perinatal or sexual. rarely faeco-oral

Question 8

characteristics of hepatitis C virus

Answer 8

enveloped RNA virus. NS1 and E proteins important

Question 9

characteristics of hepatitis C virus infection

Answer 9

incubation for 15-120 days. insidious onset. common in adults. percutaneous transmission. mostly chronic cases. can cause cancer. responsive to IFN treatment

Question 10

risk factors for contracting hepatitis C

Answer 10

IV drug users. Needle stick injury, Haemodialysis. Verticle transmission and Sexual transmission, blood transfusions before 1992

Question 11

what are the 2 big GI infections

Answer 11

norovirus and rota virus

Question 12

characteristics of norovirus

Answer 12

nonenveloped RNA virus.

Question 13

characteristics of norovirus infection

Answer 13

once exposed, 2 days for symptoms to appear. symptoms include fever, vomiting, diarrhoea, abdominal pain. common in infants and young children but all can be infected.

Question 14

treatments for norovirus

Answer 14

no antivirals available but oral vaccines are available

Question 15

characteristics of rotavirus

Answer 15

dsDNA in a triple capsid. infects cells of intestinal epithelium using surface proteins VP7 and VP4. important in attachment and entry.

Question 16

mechanism of rotavirus infection

Answer 16

binds and enters by endocytosis. loses outer layer. VP1,2,3, in virus transcribe dsDNA. mRNA enter cytoplasm and viral proteins made. then is assembly of the single and double shelled particles in the cytoplasm.
double shelled -> ER, acquires outer shell -> leaves cell to infect new cell

Question 17

what is a +ve sense virus

Answer 17

viral RNA can be directly translated by host ribosomes, no need for transcription

Question 18

what is -ve sense virus

Answer 18

viral RNA is the coding strand (for sense) and template strand .’. needs a reverse transcriptase

Question 19

characteristics of measles virus

Answer 19

enveloped -ve sense ssRNA. pleomorphic. highly contagious. transmitted via sneezing or coughing. virus can live on surface for up-to 2hrs

Question 20

characteristics of measles virus infection

Answer 20

after 2/3 days = white spots inside mouths., 3-5 days = rash on face and spreads down to feet. fever may spike.

Question 21

characteristics of mumps virus

Answer 21

enveloped ssRNA virus. transmission via droplets eg cough/sneeze

Question 22

characteristics of rubella

Answer 22

enveloped ssRNA virus from togavirus. transmission via droplets e.g. cough/sneeze

Question 23

what is rubella

Answer 23

acute viral disease with fever and a rash lasting 2-3 days, the disease is mild in children and young adults.

Question 24

what is congenital rubella

Answer 24

newborn has rubella bc pregnant mother contracted it. results in birth defects e.g. deafness, cataracts, heart defects, damage to fatal brain, liver and spleen

Question 25

what is adenovirus

Answer 25

nonenveloped dsDNA virus. commonly = respiratory illness; may cause other illnesses like gastroenteritis, conjunctivitis, cystitis and rash

Question 26

what is papillomavirus

Answer 26

non-enveloped dsDNA, some cause infection in genital tract, responsible for cervical cancer

Question 27

what is parvovirus

Answer 27

non enveloped dsDNA virus has receptor that allows it to attach to erythrocyte progenitors. parvovirus B19 = inhibition of erythropoiesis

Question 28

clinical presentation of parvovirus

Answer 28

erythema infectosum which has slapped cheek appearance on face. red rash on trunk and limbs. low grade fever, typically resolves in 7-10 days

Question 29

more serious problems that parvovirus can cause

Answer 29

gloves and shock syndrome, arthropathy, transient aplastic crisis, chronic red cell alpasia, neutropenia, pancytopenia, thrombocytopenia

Question 30

how is parvovirus transmitted

Answer 30

respiratory route via droplets. can be passed from mother to foetus.

Question 31

how do we diagnose parvovirus

Answer 31

serologically. IgM = recent virus. IgG = past infection. | also try to detect viral dna

Question 32

characteristics of influenza virus

Answer 32

airborne RNA virus. lipid envelope derived from host cell membrane. hem agglutinin and neuraminidase proteins on surface and ion channel (M2) embedded in viral envelope. has ribonucleic protein complex containing RNA and protein together.

Question 33

what is type A influenza

Answer 33

most serious and affects mammals and birds. cross over being type A strains may = pandemic. strains classified according to surface antigens

Question 34

what is type B influenza

Answer 34

Affects humans but causes only minor outbreaks not pandemics

Question 35

what is type C influenza

Answer 35

mild. affects only humans. is endemic, symptoms similar to common cold

Question 36

how does influenza A get into cells

Answer 36

attached to cells using (haemagluttinin) HA to attach to sialic acid on host cell membrane and is then internalised by endocytosis .'. is inside endosome in cell. virus envelope fuses with endosome membrane triggers uncoating of virus

Question 37

how does virus inside cell replicate itself

Answer 37

virus envelope fuses with endosome membrane =virus uncoated, viral nucleocapsid released into cytoplasm. -ve sense RNA is copied in nucleus to form +ve sense strand. copied back several times to -ve strand to be packaged into virus. mRNA synthesised from +ve sense to form viral proteins

Question 38

why down influenza A virus mutate rapidly

Answer 38

bc the RNA polymerase involved in replication of genome has a low selectivity and no proofreading mechanism .'. mistakes made often and not corrected

Question 39

what are the two patterns of mutation

Answer 39

antigenic shift and antigenic drift

Question 40

what is antigenic drift

Answer 40

continual viral mutation, often minor with no effect on function but changes accumulate over time and lead to new drifted strains that can produce illness

Question 41

what is antigenic shift

Answer 41

only occurs in type A influenza. genetic reassortment where there is mixing of genetic material between strains when they infect same host resulting in novel strain to which everyone lacks immunity

Question 42

symptoms of ebola virus

Answer 42

Fever, Headache, Diarrhoea, Vomiting, Stomach pain, Muscle pain, Unexplained bleeding or bruising

Question 43

characteristics of Ebola virus

Answer 43

enveloped RNA virus. spread by direct contact with blood or body fluids or contaminated objects e.g. needles

Question 44

how does ebola infect humans

Answer 44

enters through mucous membrane or through break in skin. infect many cell types. migrates from initial site of infection to lymph nodes, then liver spleen and adrenal gland. tissue necrosis occurs, inflammation and finally organ failure