Enveloped (-) strand RNA viruses - Aucoin

Question 1

Name the families of negative strand RNA viruses.

Answer 1

1. Rhabdoviridae
2. Filovirus
3. Orthomyxovirus
4. Paramyxovirus
5. Bunyaviridae
6. Arenaviridae

Question 2

Describe the rabies virus.

Answer 2

1. family Rhabdoviridae, genus Lyssavirus
2. broad host range, infects all mammals
3. transmitted by bite of rabid animal such as bat, raccoon, skunk
4. not common in US, 50,000 cases worldwide

Question 3

Describe the clinical course of rabies virus.

Answer 3

1. incubation phase 2 weeks to a year
2. Two phases: Prodrome phase - fever, nausea, headache, spread to CNS from muscle.
3. Neurologic phase - hydrophobia, anxiety/irritability, paralysis, coma and death. 100% mortality rate in this phase.
4. diagnosis - cytologic detection of inclusion bodies (Negri bodies) or detection of viral antigen in brain tissue (postmortem).
5. treatment - following bite of rabid animal administer vaccine and human rabies IgG.

Question 4

What is absolutely essential for neg. sense RNA virus infection and replication?

Answer 4

They must have RNA-dependent RNA polymerase in the virion particle.

Question 5

Name 2 viruses that are part of the Filoviridae family.

Answer 5

1. Ebola virus

2. Marburg virus

Question 6

Describe Ebola and Marburg viruses.

Answer 6

1. cause severe hemorrhagic fever, greater than 90% mortality rate
2. bats are the likely reservoir
3. transmitted by direct contact with contaminated body fluids
4. infects macrophages and spreads via the blood
5. tissue destruction due to release of cytokines causing vascular permeability, hemorrhage and shock
6. found in Africa

Question 7

Describe the clinical course of Ebola and Marburg virus infection.

Answer 7

1. causes severe hemorrhagic fever - sudden fever, headache, joint and muscle pain, vomiting, diarrhea.
2. eventual bleeding into skin, mucous membranes, and visceral organs.
3. death by multi-organ failure and shock.
4. no specific treatment or vaccine
5. diagnosis - immunoassay, serology, PCR

Question 8

Describe influenza virus.

Answer 8

1. family Orthomyxovirus
2. ubiquitous, may cause pandemics
3. transmitted by respiratory droplets
4. There are 3 main types - Influenza A, B, C
5. can undergo antigenic shift - reassortment of segments of the RNA genome
6. can undergo antigenic drift - small mutations in the genome RNA

Question 9

Name some cell surface proteins of Influenza virus that are important.

Answer 9

1. Nuraminidase (NA) - helps virus get out of cell
2. Hemagluttinin (HA) - helps virus get into cell
   Antigenic changes to HA and NA cause epidemics and pandemics.

Question 10

Describe some clinically important characteristics of the different types of Influenza virus.

Answer 10

1. Influenza A causes pandemics, has 16 antigenic types of HA and 9 types of NA , and can infect birds, chickens and pigs.
2. Influenza B causes outbreaks.
3. Influenza C causes mild infections.

Question 11

Describe the clinical course of Influenza virus.

Answer 11

1. incubation period of 24-48 hours
2. symptoms - sudden onset of: fever,myalgia, headache, sore throat, cough
3. elderly and those with cardiac or pulmonary disease are at high risk
4. symptoms resolve in 4-7 days
5. pneumonia is a complication
6. immunity depends on secretory IgA targeting HA in respiratory tract

Question 12

Describe the diagnosis and treatment of Influenza virus infection.

Answer 12

1. diagnosis - made on clinical grounds, lab tests are available
2. treatment and prevention - Oseltamivir (Tamiflu), and Zanamivir (Relenza)
3. Vaccines are availble - they are based on Influenza A and B and are reformulated yearly to current antigenic strains

Question 13

What are two highly virulent avian influenza pathotypes?

Answer 13

H5 and H7.

Question 14

Describe the measles virus.

Answer 14

1. family paramyxovirus, genus morbilivirus
2. characterized by a maculopapular rash
3. transmitted via respiratory droplets
4. infects respiratory tract then spreads in blood via phagocytic cells
5. 30 million cases per year worldwide
6. US cases often brought from other countries and causing infection in unvaccinated groups

Question 15

Describe the clinical course of the measles virus.

Answer 15

1. incubation period 10-14 days
2. symptoms - fever, conjuctivitis, runny nose, and cough followed by rash that spreads from face to extremities
3. diagnostic indicator - Koplick spots - small white spots on inflamed buccal mucosa, often present before rash
4. Encephalitis occurs at a rate of 1 per 1000 cases
5. prevention - live, attenuated vaccine
6. often given concurrently with MMR - called the MMRV vaccine (measles, mumps,rubella, varicella)

Question 16

Describe Parainfluenza virus.

Answer 16

1. family paramyxovirus
2. cause croup, laryngitis, bronchiolitis (infection of small airways) and pneumonia in children
3. in adults - causes disease similar to common cold
4. transmitted via respiratory droplets

Question 17

Describe the clinical course of parainfluenza virus infection.

Answer 17

1. PIV 1 and 2 are the main cause of croup in children younger than 5 years old
2. croup is characterized by a barking cough and hoarseness
3. also causes a variety of respiratory diseases cuch as the common cold, pharyngitis, laryngitis, otitis media, bronchitis and pneumonia
4. PIV 3 is seen in lower respiratory infections in children
5. most infections are diagnosed clinically
6. look for barking cough, inspiratory stridor, tachypnea, wheezing, fever, sore throat, mild cough, rhinorrhea, and respiratory distress.

Question 18

What is the steeple sign?

Answer 18

On X-ray the closed in trachea forms a point that looks like a steeple - seen in parainfluenza virus infection.

Question 19

Describe the mumps virus.

Answer 19

1. family paramyxovirus
2. causes painful swelling of the parotid gland (one or both) and other salivary glands
3. occurs primarily in childhood
4. transmitted via respiratory droplets
5. only has one serotype

Question 20

Describe the clinical course of mumps virus.

Answer 20

1. infects the upper respiratory tract and spreads via blood to parotid glands, testes,ovaries, pancreas and in some cases the meninges
2. diagnosis is clinical although some testing is available - look for parotitis, fever, malaise, difficulty speaking and chewing
3. low incidence in US
4. prevention - live, attenuated vaccine

Question 21

Describe Respiratory syncytial virus.

Answer 21

1. family paramyxovirus
2. RSV most common cause of pneumonia and bronchiolitis in infants
3. neonates, premature infants and infant with cardiopulmonary disease are susceptible (birth to age 2 most at risk)
4. transmitted via respiratory droplets

Question 22

Describe the clinical course of RSV.

Answer 22

1. adults - causes common cold and bronchitis or pneumonia in elderly
2. infants - pronounced cough and expiratory wheezing. Look for - diffuse expiratory wheezing, mild cyanosis and respiratory distress.
3. rapid antigen test detects virus in respiratory secretions
4. Ribavirin is recommended for severely ill, hospitalized infants
5. passive immunization with antibody is a treatment option

Question 23

Describe Metapneumovirus.

Answer 23

1. family, paramyxovirus
2. significant cause of acute respiratory disease in infants and children
3. second to RSV in causing bronchiolitis during winter months
4. illness comparable with symptoms and severity to RSV
5. most likely spreads via respiratory droplets

Question 24

Describe the clinical course of metapneumovirus.

Answer 24

1. causes acute respiratory disease in infants and children - look for fever, rhinorrhea, wheezing, pulmonary infiltrates, bronchiolitis and respiratory distress
2. causes mild respiratory tract infections in the general community
3. genome detection by PCR assay of respiratory secretions, rule out RSV
4. no known treatment

Question 25

Describe Hantavirus.

Answer 25

1. family, Bunyaviridae
2. causes Hantavirus fever with renal syndrome (HFRS) in Europe, Asia and Africa
3. causes Hantavirus pulmonary syndrome (HPS) in US - also called Sin Nombre virus
4. HPS endemic in deer mice in Western US - New Mexico and Arizona
5. acquired by inhalation of aerosolized rodent feces and urine
6. replication in pulmonary capillary endothelial cells

Question 26

Describe the clinical course of Hantavirus.

Answer 26

1. HPS causes flu-like symptoms followed by respiratory failure
2. HPS mortality rate high - 35%
3. diagnosis - detect viral RNA in lung tissue, PCR, immunohistochemistry - IgM
4. no vaccine or effective drugs

Question 27

Describe California encephalitis virus.

Answer 27

1. family, Bunyaviridae
2. is an arbovirus spread by mosquito
3. has a subtype called La Crosse virus that causes encephalitis
4. LACV-mediated encephalitis is most common arboviral disease in US - most cases in summer in children younger than 16

Question 28

Describe the clinical course of California encephalitis virus.

Answer 28

1. symptoms - severe headache, fever, possible vomiting, convulsions
2. half of patients develop seizures
3. morality rate is 1% by aseptic meningitis- most recover completely
4. diagnosis - serologically - IgM or IgG
5. seropositive individuals protected from re-infection
6. no vaccine or effective drugs

Question 29

Describe Crimean congo hemorrhagic fever.

Answer 29

1. family, Bunyaviridae
2. tickborne, common in Africa, Asia, Eastern Europe
3. mortality rate - 3-30%
4. outbreaks caused by handling infected mammals or humans
5. causes extensive liver damage - hepatomegaly

Question 30

Describe the clinical course of Crimean congo hemorrhagic fever.

Answer 30

1. symptoms - initial fever, headache, myalgia, dizziness and mental confusion followed by hemorrhagic phase
2. hemorrhagic phase - bleeding rom nose, GI, uterus, respiratory tract
3. diagnosis by serology
4. Ribavirin may be helpful treatment

Question 31

Describe Rift Valley fever virus.

Answer 31

1. family, Bunyaviridae
2. mosquito-borne pathogenic primarily for domestic livestock
3. most human cases zoonotic via infected livestock tissue
4. most cases in sub-Saharan Africa and Egypt with many outbreaks

Question 32

Describe the clinical course of Rift Valley Fever virus.

Answer 32

1. Causes mild febrile illness and recovery almost always complete
2. complications include retinitis, encephalitis and hemorrhagic fever
3. permanent loss of vision in 1-10% of retinitis patients and 1% mortality rate
4. diagnosis - viral isolation from tissues or serological via ELISA (looking for pt antibodies on an antigen matrix)

Question 33

Describe Lymphocytic choriomeningitis (LCM).

Answer 33

1. Family, Arenaviridae
2. transmitted by aerosol inhalation, ingestion of contaminated food
3. house mouse or hamsters are common reservoirs (secretions and excretions)
4. worldwide distribution with low mortality rate

Question 34

Describe the clinical course of LCM.

Answer 34

1. most infections are asymptomatic
2. flu-like symptoms - fever, headache, myalgia and malaise
3. can cause aseptic meningitis in minority of patients - fever, headache and stiff neck
4. no treatment or vaccine
5. diagnosis- serological testing for IgM or IgG

Question 35

Describe Lassa Fever virus.

Answer 35

1. Family Arenaviridae
2. aerosol transmission or contact with rodent excretions
3. person to person spread by contact with blood, secretions or excretions
4. endemic to West Africa, field rat is reservoir

Question 36

Describe the clinical course of Lassa Fever virus.

Answer 36

1. Causes severe hemorrhagic fever, myalgia and severe weakness
2. enters via skin abrasion or inhalation
3. replicates in lymph node
4. viremia develops and spreads systemically via macrophages
5. diagnosis - serologic testing for IgM or IgG
6. no vaccine, Ribavirin is useful treatment