Viral Respiratory Infections - DNA Viruses Flashcards
How is mucous protective of the URT?
Contains mucins which are high viscosity tot rap viral particles, and contain decoy sialic acid receptors for agglutinating the virus
What virus subfamilies are EBV, VZV, and CMV in?
All Herpesviruses
VZV = alpha herpesvirus CMV = beta herpesvirus EBV = gamma herpesvirus
Is EBV common?
Yes, in US about 50% are seropositive before age 5, with another wave in adolescents and young adults
What does EBV usually cause in young children:
Sore throat and fever
Much less commonly otitis media, GI symptoms, and mono
What are the symptoms of EBV infectious mono-nucleosis? How long does it last?
Common in adolescents and adults
Fatigue, fever, sore throat (pharyngitis, copious)
Specific: Lymphadenopathy (cervical, could be generalized), splenomegaly (due to T cell proliferation), lymphocytosis, and heterophile antibodies
Lasts 2-4 weeks acutely, with fatigue lasting longer
What are heterophile antibodies?
Antibodies recognizing unusual antigens, caused by nonspecific B cell activation by EBV infection, even though the B cells never encountered those antibodies.
How is EBV transmitted and what is its cell tropism?
Transmitted via saliva
Tropism: infection begins in epithelial cells of upper respiratory tract, and spreads to B cells
Up to 10% of peripheral B cells become infected -> heterophile antibodies
What causes lymphocytosis in EBV?
T cells responding to infection proliferate
Why can EBV be transmitted even after infection resolution?
About 1 in 1,000,000 B cells remain latently infected -> potential for subclinical virus shedding
What cancers and lymphomas is EBV associated with?
Burkitt’s lymphoma (Africans, bar kid, swelling cheeks), Nasopharyngeal carcinoma (asians), Hodgkin’s Lymphoma (Owl sitting in Reeds), Lymphomas / Lymphoproliferative tumors in AIDS
What is Hairy Oral Leukoplakia? How can this be distinguished from Candida?
White, wart-like lesions typically found on the side of the tongue, which are sites of active EBV replication
Difference from Candida: cannot be wiped off
What clinical features distinguish CMV mononucleosis vs EBV mononucleosis?
CMV mono-nucleosis will be heterophile antibody negative, but will still show hepatosplenomegaly
How is CMV transmitted?
Direct contact, sexual contact, transfusion, transplantation, breast milk, or transplacentally
What is the structure of adenoviruses and where do they replicate?
Like all DNA viruses except poxviruses, they replicate in the nucleus.
Linear, dsDNA genome, non-enveloped icosahedral
What major CMV complications are immunocompromised patients at risk for?
CMV pneumonia and retinitis
What is the cell tropism of adenoviruses?
Mucosal epithelial cells - so primarily a respiratory pathogen
Respiratory tract, small intestine, epithelial tissue of eye
What are the modes of transmission for adenoviruses?
Respiratory spread, especially GI pathogens subtype 40 and 41 can spread fecal-oral.
However, even in respiratory subtypes, the virus spreads to the GI tract and is spread in the feces (poor hygiene)
What acute respiratory infection can adenovirus cause and what is its primary complication?
Acute febrile pharyngitis -> fever, sore throat, cough, nasal congestion with possible tonsillitis (pretty nonspecific for viral pathogens)
It is highly infectious and can lead to pneumonia as a complication.
What is Acute Respiratory Disease (ARD)?
Respiratory infection commonly found in military recruits, transmission facilitate by stress and crowing.
Can cause mild URI to pneumonia
Only military has a vaccine
What is pharyngoconjunctival fever? How is it uncommonly spread?
Adenovirus infection uncommonly spread through swimming pools, but also aerosols and fomites
Pharyngo: URI
Conjunctival: Pink eye
What is epidemic keratoconjunctivitis and how is it typically spread?
Adenovirus causing highly contagious corneal and conjunctival infection which can cause permanent corneal damage, especially among those with corneal abrasion.
Typically spread via healthcare workers contamined eyedrops
What do Adenovirus types 40 and 41 cause?
Infant gastroenteritis
Most adenoviruses replicate in GI tract, but do not cause GI disease
What are two super uncommon adenovirus infections?
Urethritis and cystitis
What are the two subfamilies of Parvoviruses, and what are the general features of each?
Very small ssDNA genomes
- Parvovirinae - autonomously replicate, includes Parvovirus B19
- Dependovirinae - requires helper viruses to replicate (adenovirus or herpesvirus), not associated with any disease and are being looked at for gene vector therapies
What disease does Parvovirus B19 cause? Who gets it?
Erythema Infectiosum (Fifth Disease)
Typically school age children, rarely adults
Who is at greatest risk of severe disease from Parvovirus B19?
Immunocompromised
Fetuses
Hemolytic anemia (due to associated reticulocyte suppression)
What is the first stage of Parvovirus B19 infection / where does it replicate / shed?
Nonspecific flu-like symptoms and suppression of reticulocytes (RBCs)
Replicates in bone marrow and sheds in Upper Respiratory Tract (probably URT transmission)
Parvoviruses are inactivated by protective IgM response
What is the second phase of Parvovirus infection?
Deposition of immune complexes leads to erythematous rash + arthritis symptoms
What does Parvovirus B19 infection cause in patients with hemolytic anemia?
Transient Aplastic Crisis -> low number of RBCs until the infection is cleared
How are patients with hemolytic anemia and immunocompromization with Parvovirus B19 treated?
Hemolytic Anemia - Blood Transfusions
Immunocompromised - Immunoglobulin therapy
What is the risk in pregnancy of Parvovirus B19 infection?
Hydrops fetalis
- fatal anemia of the fetus
- condition caused by anemias which force the fetal heart to pump much more blood volume for the same amount of oxygen
