virology II

Question 1

ORF virus

Answer 1

causes localized skin infections
parapox virus
usually infects sheep/goats and their handlers
localized to a few lesions on hands and arms
lesions are PAINFUL and take weeks to heal but are self-resolving
no treatment available
vaccine for animals has been approved

Question 2

what viruses cause skin lesions and systemic infection but don’t have infectious particles in the lesions?

Answer 2

herpes 6/7, measles, rubella, parvovirus B19

Question 3

parvovirus: characteristics of the family (type, characteristics). where do they replicate? relevant human pathogen?

Answer 3

small ssDNA virus
non-enveloped icsohedral capsid
no DNA pol- only replicate in actively dividing cells. B19 is human pathogen

Question 4

Parvovirus B19: disease

Answer 4

biphasic childhood disease
early phase: flu-like illness 1 wk post infection
Later phase: (17 days post infection) rash- aka erythema infectiosum, fifth disease, or slapped cheek disease. lasts 2-4 days. may be accompanied by arthritis

Question 5

parvovirus B19 transmission and complications

Answer 5

transmission: resp. and oral secretions; placental
complications: bone marrow is a major site for replication due to affinity for P antigen. can disrupt RBC production. anemic persons may get APLASTIC CRISIS. treat with blood transfusion.
may also cause spontaneous abortion or hydrops fetalis (edema in fetal subcutaneous tissue). babies that come to term with B19 infection have no lasting complications.

Question 6

what viruses spread systemically and cause skin lesions with infectious virus?

Answer 6

HSV, VZV, coxackie, echoviruses, orthopoxviruses (cariolla, vaccinia, cowpox, monkeypox)

Question 7

cowsakie and echoviruses

Answer 7

skin rashes, enanthems. not severe. aka hand foot and mouth disease. may also cause CNS infections

Question 8

orthopoxvirus

Answer 8

enveloped dsDNA viruses
replicate in the CYTOPLASM
variola, monkeypox, cowpox, vaccinia

Question 9

variola:

Answer 9

causes smallpox
highly contagious and often fatal (30%)
four clinical subtypes: ordinary (90%), modified (in previously infected ppl), flat, and hemorrhagic
enveloped dsDNA virus

Question 10

transmission and acute infection with variola

Answer 10

transmission: person to person via droplets and/or contact with bodily fluids, lesions, scabs, clothing, air. 5-10 virus particles can cause infection.
acute infection: incubation of 3-17 days.
prodrom with fever and malais 2-4 days before rash
rash leaves scars
cause of death: secondary infections? bacterial sepsis? pneumonia? nephritis? encephalitis?

Question 11

what is the historical vs. the current smallpox vaccine?

Answer 11

historical dryvax was a live vaccinia virus cultured from calf lymph. new vaccine will be ACAM2000, which is grown in culture. MVA, which was created by many passages in chicken embryo fibroblasts, may be even safer- no replication in human cells.

Question 12

What five features can be used to distinguish smallpox from chickenpox? what are the differences?

Answer 12

incubation, prodrome, location of lesions, and scabs.
incubation is 7-17 days for sp, 17-21 for cp
smallpox has a prodrome before rash
smallpox has uniform lesions most numerous on face, arms, and legs; palms and soles too
chickenpox has non-uniform lesions on body, not palms and soles
scabs for 10-14 days post rash for small pox, and 4-7 days post rash for chickenpox

Question 13

smallpox vaccine: contraindications and complications

Answer 13

contraindications: immunocompromised person, person with eczema
complications: eczema vaccinatum- virus spreads from vaccination spot across the body. high mortality
generalized caccinia: vaccinial lesions anywhere on the body 4 days or more post vaccination. cause by viral spread through the blood. usually self-limiting but can be severe in immunocompromised people
progressive vaccinia: vaccination site doesn’t heal. may be fatal and due to immune deficiencies
post-vaccinal encephalitis: not due to direct infection of CNS
myocarditis/pericarditis

Question 14

monkeypox virus

Answer 14

resembles smallpox. endemic in rodents in Africa. outbreaks in US from pet importation. doesn’t spread easily from human to human.

Question 15

characteristics of flaviviruses and alpha viruses

Answer 15

enveloped positive ssRNA viruses

Question 16

important flaviviruses

Answer 16

yellow fever, west nile, dengue, japanese encephalitis, St. louis encephalitis

Question 17

most important cause of encephalitis worldwide

Answer 17

japanese enchephalitis

Question 18

dengue virus disease

Answer 18

transmitted by mosquites, though humans serve as a reservoir
classic dengue: flu symptoms that are followed by severe pain in muscles and jts. often see a maculopapular rash.
Dengue hemorrhagic fever: 10% fatality rate. hemorrhage into GI tract and skin. occurs in 2nd exposures to dengue. (4 viral serotypes- infection with one serotyp generates abs that protect against that type but enhance the ability of other serotypes to infect monocytes via Fc receptors. monocyte infection leads to cytokine release leading to vascular damage, shock and hemorrhage
pos sense ssRNA virus; enveloped

Question 19

yellow fever- virus characteristics and clinical stuff

Answer 19

ssRNA pos sense enveloped
severe liver damage, coagulopathy and upper GI tract hemorrhage. signficant fatality. live attenuated vaccine available but no treatment.

Question 20

fecal/oral viruses: envelope or no?

Answer 20

all viruses transmitted by the fecal oral route have no envelope

Question 21

Rotavirus: charachteristics

Answer 21

segmented dsRNA viruses
common cause of GI distress in kids
incubation 1-2 days. vomiting and diarrhea for 4-7 days. infected cells in the intestine are killed- villous atrophy. fluid and electrolyte loss with watery diarrhea.

Question 22

rotavirus vaccines

Answer 22

2 live attenuated viruses possible
Rotarix is monovalent vaccine
TotaTeq is a live oral pentavalent vaccine.

Question 23

norovirus- characteristics, disease

Answer 23

GI distress in adults
pos ssRNA
no envelope
common in group settings (cruises)
low infectious dose, shedding of virus post-recovery, resistance of virus to chlorination
vomiting and diarrhea
24-48 hrs

Question 24

hepatitis A: type, mode of infection, incubation

Answer 24

ssRNA non-enveloped
fecal oral rout
2-4 wks
esp. common in developing countries. disease milder in kids

Question 25

Heptatitis A disease

Answer 25

infects the GI tract, then enters the blood and goes to the liver. liver cells are damaged. long incubation period (2-5 wks). jaundice more common in adults.
inactivated virus vaccine available

Question 26

hepatitis E type mode of infection, incubation

Answer 26

ssRNA pos sense
non-enveloped
fecal-oral rout
may be waterborne
long incubation: 6-8 wks
generally mild disease but v. dangerous in preg. women.

Question 27

hepatitis B: type, mode of infection, incubation,carrier info

Answer 27

dsDNA
blood borne/sex (blood, semen, milk, saliva)
6 wks-6mo
carriage associated with liver cancer

Question 28

Heptatis B replication, virion components

Answer 28

replication via RNA intermediate that uses reverse transcriptase
virion components: HBsAg (surface antigen), HBcAg (core antigen), HBeAg (e antigen- marker for active replication)

Question 29

hepatitis B acute infection and pathogenesis

Answer 29

long incubation (6 wks-6 mo). then, mild fever and non-specific symptoms.  icteric phase of 1-2 months.  jaundice and acute liver symptoms, or, rarely, fulminant hepatitis (80% mortality)
virus infects hepatocytes.  liver cells killed by CD8 Tcells.  then Abs to HBsAg appear to prevent reinfection.  90% of adults clear the infection

Question 30

hepatitis B chronic infection and diagnosis

Answer 30

virus carriers. most common in immune deficient persons or ppl infected at a young age. can cause cirrhosis or hepatocellular carcinoma
detect chronic infection with presence of HBsAg and HBeAg in blood for prolonged time. detection of anti-HBsAg antibodies by ELISA uncommon in people who have chronic infection (abs are bound to ags in that case)

Question 31

hepatitis B prevention and treatment

Answer 31

prevention: vaccine. this is a multistep vaccine
treatment: alpha interferon, inhibitors of viral reverse transcriptase like lamivudine and adefovir

Question 32

hepatitis D: charachteristics, viral factors, infection scenarios

Answer 32

circular neg ssRNA
HBsAg as its envelope
transmitted like hep B (blood-borne; sex; needles)
can cause a more severe acute hep B infection with higher risk of fulminant hep and chronic infection
can be chronic infection with hep B and incr. risk of cirrhosis and hepatocellular carcinoma
can cause severe acute infection

Question 33

hepatitis C- characteristics, epi, transmission

Answer 33

enveloped pos ssRNA virus
blood-borne transmission, mostly by IV drug use.
SEXUAL AND VERTICAL TRANSMISSION V. RARE

Question 34

hepatits C: acute and chronic infections;

Answer 34

incubation of acute infection 204 mo. often sublinical

75% of infections are chronic. liver cirrhosis elevated and so is HCC. liver damage is immune mediated

Question 35

hepatitis C treatment

Answer 35

ribavirin plus IFN-alpha in combination