Flashcards in Orthomyxoviridae And Paramyxoviridae Deck (38):
What is the virus that is included in orthomyxoviridae?
What are the viruses that are included in Paramyxoviridae?
1. Parainfluenza virus
4. Mumps virus
5. Measles (rubeola) virus
What percentage of the entire world population gets infected with the influenza virus every year?
Describe briefly the structure of orthomyxoviridae.
1. Spherical virions
2. At the center lie 8 segments of negativ (-) stranded RNA put together with a protein (nucleocapsid protein - NP) into a helical symmetry.
3. Surrounding the nucleocapsid lies an outer membrane studded with long glycoprotein spikes.
What are the two distinct types of glycoproteins?
1. One with Hemagglutinin Activity (HA)
2. One with Neuraminidase Activity (NA)
What are the M proteins?
Anchoring the bases of these glycoprotein spikes on the inside of the viral lipid bilayer are membrane proteins. (M proteins)
What is the role of hemagglutinin?
1. Can attach to sialic acid receptors - RBCs.
2. Also on upper respiratory tract cell membranes.
3. So hemagglutinin is essential for adsorption.
What will antibodies against hemagglutinin cause?
They will block the binding of the virus and prevent infection.
What is the action of neuraminidase?
Neuraminic acid is an important component of mucin, a substance overlying mucosal epithelial cells.
This enzyme cleaves neuraminic acid and disrupts the mucin barrier, exposing the sialic acid binding sites beneath.
How many types of influenza virus exist?
Three - A,B,C
What is the antigenic drift?
During viral replication mutations can occur in the HA or NA, leading to changes to the antigenic nature of these glycoproteins. The changes are small.
What occurs with antigenic shift?
Complete change of the HA and NA. This can only occur with influenza type A, because the mechanism involves the trading of RNA segments between animal and human strains.
What are the main complications of influenza?
1. Pneumonia in the immunocompromised.
2. Also lowers the host defenses against many bacteria - S.aureus, S.pneumoniae.
3. New fever or failure to improve means DANGER.
What are the 4 broad categories of diagnostic tests for influenza?
1. Virus isolation
2. Detection of viral proteins
3. Detection of viral nucleic acid (RNA)
4. Serological diagnosis: 4-fold increase in specific antibody levels over 2 weeks.
The structure of paramyxoviridae is very similar to that of the orthomyxoviridae. What are the differences?
1. The negative stranded RNA is in a single strand, not segmented.
2. HA and NA are a part of the same glycoprotein spike, not 2 different spikes.
3. They possess a fusion (F) protein that causes the infected host cells to fuse together into multinucleated giant cells.
What are the 5 paramyxoviridae that cause human disease?
1. Parainfluenza virus
4. Mumps virus
5. Measles virus
What is the big picture of Paramyxoviridae?
1. Think lungs
2. Think kids
3. Think viremia
What does the parainfluenza virus cause?
1. Cold symptoms such as rhinitis, pharyngitis, sinus congestion.
2. Bronchitis and flu-like illness.
3. Children, elderly, immunocompromised suffer from lower respiratory tract infections (pneumonia).
What is the Croup?
A parainfluenza infection of the larynx and upper respiratory structures (laryngotracheobronchitis) that occurs in children.
Swelling of these structures produces airway narrowing.
Why RSV is called RSV?
RSV is so-named because it causes respiratory infections and contains an F-protein that causes formation of multinucleated giant cells (syncytial cells).
What is the main difference of RSV from the rest of its kin?
RSV lacks both the HA and NA glycoproteins.
What is the number one cause of pneumonia in young children, especially in infants less than 6 months of age?
When was metapneumovirus first isolated?
What is the 2nd MC etiology of lower respiratory infections in young children?
What can metapneumovirus cause?
1. Bronchiolitis (50%)
2. Croup (20%)
3. Pneumonia (<10%)
Where does mumps virus replicate?
In the upper respiratory tract and in regional lymph nodes - spreads via the blood to distant organs.
What are the organs particularly involved in mumps?
Infection can occur in many organs but the most frequently involved is the parotid gland.
What percentage of infected by mumps males who have reached puberty can develop orchitis?
What else can mumps virus cause?
1. Infertility (rare)
2. Meningitis (more common + more severe)
How many antigenic types of mumps virus exist?
There is only one type.
A live attenuated viral vaccine is a part of the trivalent measles-mumps-rubella (MMR) vaccine.
How is measles virus transmitted?
It is highly contagious and spreads through nasopharyngeal secretions by air or by direct contact.
Where does the virus multiply?
In the respiratory mucous membranes and in the conjunctival membranes.
How long does the incubation of measles virus last?
2 weeks prior to the development of the rash.
What are the symptoms of the prodrome phase of measles virus?
2. Swelling of the eyelids
4. High fevers to 105F
5. Hacking cough
What are the Koplik's spots?
A day or 2 before the rash, the patient develops small red-based lesions with blue-white centers in the mouth.
Think of a cop licking a red-white-blue lollipop.
Describe the measles rash.
1. Red, flat to slightly bumpy (maculopapular).
2. It spreads out from the forehead to the face, neck, and torso, and hits the feet by the third day.
Mention some complications of measles.
2. Eye damage
3. Heart involvement (myocarditis)
4. Encephalitis - most feared - 10% who develop this will die.