Enveloped (+) strand RNA viruses - Aucoin

Question 1

Name some viruses that are part of the family Togavirus.

Answer 1

1. Rubivirus

2. Alphavirus

Question 2

Describe Rubella virus.

Answer 2

1. family togavirus, genus rubivirus.
2. spread via respiratory droplets and transplacentally.
3. eliminated in US, endemic in developing countries.
4. also called German measles.

Question 3

Describe the clinical course of Rubella virus.

Answer 3

1. initial replication in the nasopharynx and local lymph nodes, spreads via blood to internal organs and skin.
2. children - usually mild - rash, low fever, nausea and mild conjunctivitis.
3. congenital rubella syndrome - spread transplacentally - causes significant malformations of baby.
4. diagnosis - detection of IgM and 4-fold rise in IgG titers.
5. live attenuated vaccine available and protective for at least 10 years.

Question 4

What are arboviruses?

Answer 4

Viruses spread by arthropod vectors. Mosquitoes are a common vector. They often cause fever, headache, and malaise. Encephalitis and hemorrhagic fever may also occur.

Question 5

Name the genus’ that include arboviruses.

Answer 5

1. Togaviruses
2. Flaviviruses
3. Bunyaviruses

Question 6

Describe Eastern equine encephalitis virus.

Answer 6

1. family togavirus, genus alphavirus.
2. mosquito vector
3. reservoir - wild birds
4. 33% mortality rate, rare
5. epizootics (viral disease in a group of animals) in horses have occurred regularly in US

Question 7

Describe the clinical course of eastern equine encephalitis virus.

Answer 7

1. symptoms - severe headaches, nausea, vomiting, fever, changes in mental status, seizures and coma can occur.
2. survivors are left with brain damage.
3. diagnosis - isolating virus or detecting rise in Ig titer.
4. no antiviral or vaccine available for humans.

Question 8

Describe western equine encephalitis virus.

Answer 8

1. family togavirus, genus alphavirus.
2. mosquito vector
3. reservoir - wild birds
4. 2% mortality rate
5. diagnosis via isolating virus or detecting rise in Ig titer
6. no vaccine for humans, no antivirals available
7. predominately found West of Mississippi and in S. America.
8. disease is similar to eastern encephalitis but less severe.

Question 9

Describe Venezuelan equine encephalitis virus.

Answer 9

1. family togavirus, genus alpahvirus.
2. mosquito vector
3. equine réservoir
4. predominately found in S. and Central America but has spread to US

Question 10

Describe the clinical course of Venezuelan equine encephalitis virus.

Answer 10

1. healthy adults get flu-like symptoms - high fever, headache.
2. those with weakened immune systems can die.
3. there is a vaccine available to humans.
4. only at risk military and lab personnel are vaccinated in US.

Question 11

Name all the viruses that are part of the alphavirus genus.

Answer 11

1. Eastern equine encephalitis virus.
2. Western equine encephalitis virus.
3. Venezuelan equine encephalitis virus.

Question 12

Name all the viruses that are a part of the family Flaviviridae.

Answer 12

1. Dengue virus
2. St. Louis encephalitis virus
3. West nile virus
4. Yellow fever virus
5. Hepatitis C virus

Question 13

Describe Dengue virus.

Answer 13

1. family Flaviviridae
2. arbovirus - spread by mosquitoes
3. endemic in SE Asia, Central and S. America and Caribbean.
4. 4 serotypes
5. imported cases common in US.

Question 14

Describe the clinical course of Dengue virus.

Answer 14

1. symptoms - acute fever, headache, retroocular pain, rash, myalgia and bone pain.
2. also called ‘breakbone fever’, rarely fatal.
3. Can progress to hemorrhagic fever - GI and skin hemorrhage, shock and coma. Has 10% mortality rate if progresses.
4. Serological IgM diagnosis, no vaccine or treatment options.
5. if pt has ever been infected with one serotype then if infected again with another serotype then are more likely to get hemorrhagic fever.

Question 15

Describe West Nile virus.

Answer 15

1. family Flaviviridae
2. arbovirus spread by mosquitoes to birds (especially crows) and humans.
3. children and elderly at higher risk.
4. virus inoculated into blood, spreads via monocytes/macrophages and brain is target organ.

Question 16

Describe the clinical course of West Nile virus.

Answer 16

1. less than 1% are symptomatic with serious neurological illness.
2. Symptoms - range from flu-like to encephalitis- nausea, headache, high fever, malaise, myalgia, backache, neck stiffness.
3. no vaccine or specific treatment available.
4. diagnosis- detection of virus-specific IgM in serum or CSF.

Question 17

Describe St. Louis encephalitis virus.

Answer 17

1. family Flaviviridae
2. arobvirus spread by misquitoes.
3. reservoir - wild birds, birds have no symptoms.
4. outbreaks occur throughout US in late summer and early Fall.
5. mainly affects US.

Question 18

Describe the clinical course of St. Louis encephalitis.

Answer 18

1. symptoms range from flu-like to encephalitis.
2. more serious neuroinvasion infections cause headache, nausea, high fever, malaise, myalgia, backache, neck stiffness.
3. mortality rate from 3-30% with elderly at risk.
4. diagnosis - IgM in serum or CFS.

Question 19

Describe Yellow fever virus.

Answer 19

1. family Flaviviridae
2. arbovirus - mosquito vector
3. endemic to Africa and S. America not US

Question 20

Describe the clinical course of Yellow fever virus.

Answer 20

1. causes hemorrhagic fever characterized by jaundice, fever, headache, myalgia, black vomit and hemorrgahes.
2. mortality rate is 20-50%.
3. diagnosis - presence of IfM.
4. no specific treatment, however highly effective live attenuated vaccine is available.

Question 21

Describe the Hepatitis C virus.

Answer 21

1. family Flaviviridae
2. transmitted parenterally
3. IV drug users and organ transplant recipients are at high risk
4. HCV associated cirrhosis is most common indication for liver transplant
5. HCV infects hepatocytes and causes liver injury from cytotoxic T cells.

Question 22

Describe the clinical course of Hepatitis C virus.

Answer 22

1. primary infections are asmyptomatic or very mild illness.
2. acute infection - decreased appetite, fatigue, nausea, muscle/joint pains, weight loss.
3. chronic hepatitis develops in 75% of patients and may progress to cirrhosis - dark urine, abdominal pain, hepatomegaly, jaundice.
4. liver cirrhosis pt’s are predisposed to hepatocellular carcinoma.
5. diagnosed by PCR for virion RNA and can monitor IgG levels for chronic infection.
6. treated with Sovaldi IFN (inhibits HVC polymerase), and Ribavirin but no vaccine available.

Question 23

What clinically important virus is part of the family Coronaviridae?

Answer 23

Coronavirus.

Question 24

Describe Coronavirus.

Answer 24

1. family Coronaviridae
2. 2nd to rhinovirus for causing common cold and separate Coronavirus may cause SARS (severe acute respiratory syndrome).
3. transmitted by respiratory aerosol.

Question 25

Describe the clinical course of Coronavirus.

Answer 25

1. cold caused by coronavirus - runny nose, sore throat, low grade fever.
2. limited to infection of mucosal cells of the respiratory tract.
3. SARS symptoms are flu-like - fever, dyspnea and hypoxia.
4. atypical pneumonia caused by SARS is characterized by diffuse edema resulting in hypoxia.