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Flashcards in Viruses Deck (125)
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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


CSF findings in aseptic (nonbacterial) meningitis

Normal glucose
No organisms
Elevated protein


What are the TORCHeS infections?

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

TOxoplasma gondii


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

It brings its own RNA polymerase


All negative-sense RNA viruses are single stranded except _____

Reovirus (includes rotavirus and colorado tick fever virus)


What are the segmented viruses?

What is the significance of segmented viruses?



Segmented viruses undergo antigenic variation


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)


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


Where do viruses replicate in host cells?

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


T/F: all herpesviruses are enveloped



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


Transmission of Picornaviridae family of viruses

Fecal-oral (EXCEPT rhinovirus which is respiratory droplets)


3 clinical subgroups of Picornaviridae

Hepatitis A —> HSM

Enteroviruses (poliovirus, coxsackie A and B, echovirus)

Rhinovirus —> common cold


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


Clinical manifestations of type A coxsackie virus

Hand, foot, and mouth disease

Red, vesicular rash

Aseptic meningitis

Infection more common in summer months


Clinical manifestations of type B coxsackie virus

Dilated cardiomyopathy

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


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


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


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


Characteristics of Caliciviridae (norovirus)

Positive sense ssRNA virus

Produces long polyprotein - cleaved into infectious subunits by viral proteases


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


Characteristics of Flaviviridae family of viruses

Positive sense RNA virus


What diseases are caused by the Flaviviridae family of viruses?

Hepatitis C
Dengue fever
Yellow fever
West Nile Virus


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


Vector and Clinical presentation of Yellow fever

Vector = aedes mosquito

Causes jaundice, backache, bloody diarrhea, hematemesis


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


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


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


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


Characteristics of Togaviridae family (equine encephalitis, rubella)

Positive sense RNA virus

Long polyprotein precursor cleaved by proteases into infectious subunits

Most are arboviruses = arthropod vector (mosquitos)