AuCoin 5: - strand enveloped RNA viruses Flashcards
What do - sense RNA viruses REQUIRE for replication in the cytoplasm?
RNA-dependent RNA polymerase
What is the only important Rhabdovirus? What does it infect? How is it transmitted?
Rabies virus (Lyssavirus); broad range of hosts - infects all mammals; transmitted via bite of rabid animal (bats, racoons, skunks)
What are the three stages of rabies virus infection?
- incubation period for 2 weeks to a year
- prodrome phase: fever, nausea, headache, spreads to CNS
- neurologic phase: hydrophobia, anxiety, paralysis, coma
How do you treat a rabies virus patient?
give vaccine and human rabies IgG following animal bite
How do you clinically diagnose rabies virus?
cytological detection of inclusion bodies or identify viral antigen in brain tissue
Ebola are Marburg viruses are filoviruses. What do they cause?
severe hemorrhagic fever
How are ebola and marburg viruses transmitted? What is the reservoir? What happens after initial infection?
by direct contact with contaminated body fluids; bats; infects macrophages and spreads via blood causing tissue destruction due to release of cytokines causing vascular permeability, hemorrhage, shock
Describe how ebola and marburg virus presents clinically leading up to death.
severe hemorrhagic fever: sudden fever headache joint and muscle pain vomiting diarrhea **bleeding into skin, mucous membranes and visceral organs death by multiorgan failure and shock
What is another name for orthomyxovirus?
influenza virus
What is on the surface of the influenza virus? What does this bind to on respiratory epithelial cells?
HA (hemagluttinin) - surface glycoproteins bind to sialic acid receptors on respiratory epithelial cells
Describe the process of influenza virus endocytosis and ultimately budding from the plasma membrane of the host cell.
- receptor mediated endocytosis of virus via HA binding to sialic acid receptors on respiratory epithelium
- segmented ribonucleoproteins are released into the cytoplasm
- genome is transported to the NUCLEUS where replication and transcription occurs
- viral mRNAs are transported to the cytoplasm for translation
- early viral replication proteins are transported back to the nucleus
- assembly and budding occurs at the plasma membrane
Why does influenza kill thousands per year?! How is it transmitted?
transmitted by respiratory droplets - infects birds, chickens, pigs; there are 3 strains A, B, C. Type A alone has 16 antigenic types of HA and 9 types of NA. Antigenic changes to HA and NA cause epidemics and pandemics.
What is this?
reassortment of segments of the genome RNA
vs
small mutations in the genome RNA
antigenic shift; antigenic drift
How does influenza typically present? When does it resolve?
incubation period of 24-48 hours, followed by: fever myalgia headache sore throat cough
**symptoms resolve in 4-7 days, but it may be complicated by pneumonia
Who is especially at risk of influenza?
elderly
patients with cardiac and pulmonary disease
How is the flu treated? How is it prevented?
prevented by new antigenic vaccine each year; immunity depends on IgA to specific HA in the respiratory tract; treated with tamiflu and relenza
This is a paramyxovirus characterized by a maculopapular rash
morbillivirus - measles virus
How is measles virus transmitted? How does it spread in the body?
transmitted via respiratory droplets; infects resp tract then spreads to blood via phagocytic cells
How does measles virus present?
incubation phase of 10-14 days, followed by:
fever
conjunctivitis
runny nose and cough
RASH that spreads from face to extremities
KOPLICK spots (small white spots on inflamed buccal mucosa)
encephalitis may occur
What are two characteristic features of measles?
Koplick spots
**white spots in mouth
rash from face to trunk
How do we currently prevent measles?
live, attenuated vaccine
Another paramyxovirus is the parainfluenza virus. What does this virus cause? How is it transmitted?
In children: croup laryngitis/pharyngitis bronchiolitis pneumonia otitis media **disease resembles a common cold in adults; transmitted via respiratory droplets
Which strains of parainfluenza virus are the main cause of croup in children younger than 5? What is croup?!
PIV 1 & 2; croup is a harsh, barking cough and hoarseness caused by swelling of the trachea and larynx
**PIV 3 is in lower respiratory infections in children
Another paramyxovirus is mumps virus. What does this cause? How is it transmitted?
causes painful swelling of the PAROTID gland; transmitted via respiratory droplets
**occurs in childhood, only a single serotype
Once in the respiratory tract, where else can mumps virus spread?
can spread via blood to parotid glands, testes, ovaries, pancreas, meninges
This paramyxovirus is the most common cause of pneumonia and bronchitis and infants; transmitted via respiratory droplets
RSV - respiratory syncytial virus
What does RSV cause in infants? In adults?
pronounced cough and expiratory wheezing in infants; common cold, bronchitis in adults; pneumonia in elderly
What is one medication used for severely ill hospitalized infants with RSV?
ribavirin
Who is specifically at risk of RSV infection?
neonates
premature infants
infants with CARDIOPULMONARY disease
This paramyxovirus is the second leading cause of bronchiolitis behind RSV; its illness is comparable to that caused by RSV; most likely spread via respiratory droplets
metapneumovirus
What does metapneumovirus cause in infants and children?
acute respiratory distress - mild resp tract infections
How does metapneumovirus differ from RSV?
it occurs in slightly older children and causes less severe disease
**if it’s not RSV, think metapneumovirus
What kind of virus is hantavirus?
bunyavirus
What does hantavirus cause?
hantavirus fever with renal syndrome
hantavirus pulmonary syndrome
Where is hantavirus pulmonary syndrome seen in the US? How is it acquired?
In Western US in DEER MICE; acquired by inhalation of aerosols of rodent feces and urine
**hanta the mouse
What are the symptoms of hantavirus pulmonary syndrome?
influenza like symptoms followed by respiratory failure
**very high mortality rate
How do you diagnose hantavirus clinically?
you detect viral RNA in lung tissue
PCR
Another bunyavirus is California encephalitis virus. What causes this? What is the most common subtype of this virus that causes disease?
it is an arbovirus - mosquito; La Crosse virus
What are the symptoms of California encephalitis virus or LCVA?
severe headache fever vomiting/convulsions seizures 1% die from aseptic meningitis
If an individual tests positive for IgM or IgG to California encephalitis virus antigen, what does this mean?
seropositive individuals are protected from re-infection
This is a disease caused by bunyavirus; it is a TICK-borne viral disease common in Africa, Eastern Europe and Asia
Crimean congo hemorrhagic fever
What causes Crimean congo hemorrhagic fever?
handling infected mammals or humans
What are the symptoms of Crimean congo hemorrhagic fever?
initially: fever headache aches dizziness mental confusion next: hemorrhagic phase bleeding from nose GI uterus
causes hepatomegaly
This is another Bunyavirus; mosquito borne; infects domestic LIVESTOCK; mostly in sub-Saharan Africa and Egypt
Rift Valley fever virus
What are the symptoms of Rift Valley fever virus?
mild febrile illness
can cause retinitis and permanent vision loss
Lymphocytic choriomeningitis is caused by an arenavirus. How is it transmitted? What is the most common reservoir?
aerosol inhalation or ingestion of contaminated food; HAMSTERS (secretions and excretions)
What do infections with arenavirus causing lymphocytic choriomeningitis present like? Do many patients with this disease die?
most are asymptomatic
influenza like symptoms
aseptic meningitis; no - low case fatality rate
So when you think lymphocytic choriomeningitis, what do you think of?
HAMSTERS
Another arenavirus is Lassa fever virus. How is this transmitted? How does it spread from person to person? How does it enter the body?
aerosol or contact with rodent excretions; spreads via contact with blood, secretions, and excretions; enters through inhalation or through skin abrasion
Where is Lassa fever virus endemic?
in West Africa
Lassa, Nigeria
What symptoms does Lassa fever virus cause?
severe hemorrhagic fever
myalgia
severe prostration
viremia can develop and it can spread systemically via macrophages
List the 6 helical - ssRNA strand viruses
arenavirus bunyavirus: bunya and hanta filovirus orthomyxovirus paramyxovirus rhabdovirus
ABFOPR
