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Flashcards in Viruses Deck (125)
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1

What does it mean for a virus to be “positive sense”?

Similar to an mRNA, it is ready for translation and does not need to bring along extra machinery (solely uses host machinery)

In general, all positive-sense RNA viruses replicate in the cytoplasm

2

CSF findings in aseptic (nonbacterial) meningitis

Normal glucose
No organisms
Elevated protein

3

What are the TORCHeS infections?

Cross the placenta and cause infection in utero —> congenital disease

TOxoplasma gondii
Rubella
CMV
HIV and HSV
Syphilis

4

What does it mean for an RNA virus to be “negative-sense”?

It brings its own RNA polymerase

5

All negative-sense RNA viruses are single stranded except _____

Reovirus (includes rotavirus and colorado tick fever virus)

6

What are the segmented viruses?

What is the significance of segmented viruses?

BOAR:

Bunyavirus
Orthomyxovirus
Arenavirus
Reovirus

Segmented viruses undergo antigenic variation

7

What are the 2 types of mutations associated with antigenic variation of viruses?

Antigenic shift: reassortment of different combos of HA and NA leading to new species; associated with PANDEMICS

Antigenic drift: point mutations in HA or NA, associated with epidemics (this is the reason for new flu shot each year)

8

Why is aspirin contraindicated in kids with suspected viral illnesses? What is the pathogenesis?

Can lead to Reyes syndrome — characterized by fever, rash, vomiting, liver failure, and encephalitis (can be fatal)

Result of OxPhos uncoupling in hepatocyte mitochondria

9

Where do viruses replicate in host cells?

In general, DNA viruses replicate in the nucleus and RNA viruses replicate in cytoplasm

10

T/F: all herpesviruses are enveloped

True

11

General characteristics of Picornaviridae family of viruses

Positive sense RNA virus
Naked (lack viral envelope)

Translated into polyprotein product and viral proteases cleave into infectious subunits

12

Transmission of Picornaviridae family of viruses

Fecal-oral (EXCEPT rhinovirus which is respiratory droplets)

13

3 clinical subgroups of Picornaviridae

Hepatitis A —> HSM

Enteroviruses (poliovirus, coxsackie A and B, echovirus)

Rhinovirus —> common cold

14

Is poliovirus acid-stable or acid-labile? What does this mean for pathogenesis?

Acid stable — survives in GI tract and infects Peyer’s patches (takes 2-3 weeks)

Then spreads to anterior horn of spinal cord causing asymmetric paralysis (often of LEs)

Also causes myalgias, decreased DTRs, aseptic meningitis, and respiratory insufficiency due to paralysis of diaphragm

15

Clinical manifestations of type A coxsackie virus

Hand, foot, and mouth disease

Red, vesicular rash

Aseptic meningitis

Infection more common in summer months

16

Clinical manifestations of type B coxsackie virus

Dilated cardiomyopathy

“Devil’s grip” (Bornholm’s disease/pleurodynia) — unilateral, sharp, lower chest pain —> difficulty breathing

17

Is Rhinovirus acid labile or acid stable? What does this mean for its pathogenesis?

Acid labile — cannot survive GI tract. It is transmitted via inhalation - which may occur via fomites (on dirty hands)

Virus attaches to ICAM-1

The virus also grows best in cooler temps (33 C), so it colonizes upper respiratory tract which acts like an air conditioner

18

Besides being positive sense RNA, naked, fecal-orally transmitted virus, what are some other characteristics of Hepatitis A virus in terms of acid stable vs. labile, and how humans come into contact with it?

Acid stable

Shed in feces, so it can contaminate the water supply in developing countries. In developed countries, it can be found in uncooked shellfish that were caught in contaminated water from developing countries.

It is commonly seen in traveler’s to endemic areas

19

Clinical features of Hepatitis A

Often clinically silent, can even be anicteric (kids usually present this way)

Active infection = fever, hepatomegaly, jaundice; symptoms last roughly 1 month

There is no carrier or chronic state

Note that smokers with Hep A develop aversion to tobacco

20

Characteristics of Caliciviridae (norovirus)

Positive sense ssRNA virus
Naked

Produces long polyprotein - cleaved into infectious subunits by viral proteases

21

Where is norovirus commonly found and what is its clinical presentation?

Often occurs with many people in close quarters — 90% of cruise ship diarrheal illness! Also occurs in daycare, schools, or with consumption of shellfish at buffets.

Causes viral gastroenteritis —> explosive, watery diarrhea

22

Characteristics of Flaviviridae family of viruses

Positive sense RNA virus
Enveloped
Non-segmented

23

What diseases are caused by the Flaviviridae family of viruses?

Hepatitis C
Dengue fever
Yellow fever
West Nile Virus

24

Characteristics of Dengue fever

Vector = aedes mosquito

Infects bone marrow; 4 types of Dengue, but type II is most important — known as “break-bone fever”

Causes thrombocytopenia and subsquent bleeding, so it is a hemorrhagic fever. Can eventually lead to renal failure and death

25

Vector and Clinical presentation of Yellow fever

Vector = aedes mosquito

Causes jaundice, backache, bloody diarrhea, hematemesis

26

Clinical features of West Nile virus including reservoir and vector, major complication, and diagnosis

Reservoir = birds
Vector = mosquitos

Major complication = encephalitis; also causes myelitis leading to flaccid paralysis, seizures, and coma

Dx by PCR and serology

27

Hepatitis C, belonging to the Flaviviridae family, is a positive sense RNA virus and is enveloped. What is its mechanism of transmission?

Most common method of transmission is via exposure to infected blood — can be through blood transfusion, IV drug use/needle-sharing, accidental needle-sticks, etc.

Can also be transmitted across placenta, sexual transmission (although Hep B is more common this way), or breastfeeding

28

What allows for antigenic variation of Hepatitis C virus if it is non-segmented?

It has no proofreading 3-5 exonuclease activity in viron-encoded RNA polymerase, so there are frequent mutations

29

Clinical findings in Hepatitis C infection

Acute: jaundice, RUQ pain, hepatomegaly, increased liver enzymes (ALT will rise and fall within 6 months)

Chronic (note that 60-80% of cases become chronic): cirrhosis, hepatocellular carcinoma

Associated with cryoglobulins = serum proteins containing IgM that precipitate in cool temps

30

Characteristics of Togaviridae family (equine encephalitis, rubella)

Positive sense RNA virus
Enveloped

Long polyprotein precursor cleaved by proteases into infectious subunits

Most are arboviruses = arthropod vector (mosquitos)