Respiratory Viruses II

Question 1

How do the genetics of paramyxoviruses differ from those of orthomyxoviruses?

Answer 1

–non-segmented negative sense ss RNA genome

–little genetic variation

Question 2

What are the three subfamilies of paramyxoviruses, and what are representative species of each?

Answer 2

–Paramyxovirinae
Parainfluenzavirus 1-4; Mumps
Morbillivirus: Measles; Canine Distemper Virus

-Pnuemovirinae
Respiratory Syncytial Virus (RSV)

–Megamyxovirinae	
Hendra virus (recently isolated from horses and humans in Australia)
Nipah virus (recently isolated from pigs and humans in Malaysia)

Question 3

What are the seven proteins of paramyxoviruses?

Answer 3

•H and N - hemagglutinin + neuraminidase activities;
–Measles - referred to as H protein - no neuraminidase activity;
–RSV - G protein - neither activity.

•F - (fusion) consists of 2 disulphide-linked subunits (F1 + F2)
- responsible for cell fusion + hemolytic function.

• M- Matrix protein lines the inner surface of the envelope.
• NP - nucleoprotein.
• L and P - polymerase activity

Question 4

Where in the cell do paramyxoviruses replicate and what determines the cells that they infect?

Answer 4

Replicate in cytoplasm (compare to Influenza-uses nucleus)

Receptors determine tropism:
e.g. CD46 (complement receptor) is receptor for measles virus
Found widely distributed throughout host

Question 5

What diseases are commonly associated with paramyxoviruses?

Answer 5

croup
URI
Bronchitis
pneumonia

Question 6

What diseases result from infection with RSV?

Answer 6

Bronchitis
Pneumonia
Croup

Question 7

What disease results from infection with Parainfluenza Virus 1 (PIV-1)?

Answer 7

Croup

Question 8

What is the most common cause of bronchiolitis and pneumonia in the first year of life? How does this present?

Answer 8

• Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis and pneumonia among infants and children under 1 year of age.
• Illness begins most frequently with fever, runny nose, cough, and sometimes wheezing. During their first RSV infection, between 25% and 40% of infants and young children have signs or symptoms of bronchiolitis or pneumonia, and 0.5% to 2% require hospitalization.

Question 9

How does measles typically cause death?

Answer 9

Most acute measles deaths are owing to secondary infections that result from a poorly understood measles-induced suppression of immune responses

Mortality is highest in girls

Question 10

What is the common presentation of measles?

Answer 10

After a 10-12 day incubation period: dry cough, sore throat, high fever, conjunctivitis (virus may be excreted during this phase), followed a few days later by the characteristic red, MACULOPAPULAR RASH and Koplik’s spots - raised red spots with white centers in the mouth.

Question 11

Define and differentiate between macules, papules, vesicles, and pustules. Which are associated with measles, and which with chicken pox?

Answer 11

•Macules, papules, vesicles or pustules
–Macules: local dilation of dermal blood vessels and become:
–Papules: when edema and cellular infiltration are present
–Vesicles: if epidermis is involved and become:
–Pustules: if inflammatory reaction

• Measles: maculopapular rash: not important for transmission
• Chicken pox, pox virus: Vesicular/pustules: important for transmission

Question 12

What three adverse events are associated with measles infection of pregnant women?

Answer 12

•Infection of pregnant women with MV can result in
–Premature labor
–Spontaneous abortion
–Low-birth weight infants

Question 13

How is the mumps virus spread, and what is the sequence of tissues infected?

Answer 13

•Humans are believed to be the only natural reservoir for the virus

• Transmission via saliva and respiratory secretions
–less infectious than measles/chickenpox - more adult cases.

•Primary replication of the virus in epithelial cells of the U.R.T. and local lymph nodes, followed by viremia.

Question 14

How does mumps present and what are the potential sequelae?

Answer 14

•Typically causes painful swelling of parotid glands 16-18 days after infection.
–In children, mumps is usually self-limited

In adults (post-puberty) a proportion of cases have more serious sequalae: 
orchitis (20-30% of males - rarely resulting in sterility); 

Less than 1% adult cases:
meningitis, 
encephalitis, 
pancreatitis, 
myocarditis, 
nephritis

Question 15

What virus subfamily does SARS belong to?

Answer 15

Coronavirus

•Severe acute respiratory syndrome (SARS) is a viral respiratory illness caused by a coronavirus, called SARS-associated coronavirus (SARS-CoV). SARS was first reported in Asia in February 2003. Over the next few months, the illness spread to more than two dozen countries in North America, South America, Europe, and Asia before the SARS global outbreak of 2003 was contained.