Respiratory Tract Viruses Flashcards
1
Q
What is the 4th most common cause of death in US?
A
-lower respiratory tract
2
Q
Who is at greatest risk for acute viral respiratory disease?
A
- the very young
- the elderly
- the chronically ill
- those with immune compromise
- *affects all age groups, but these people more so**
3
Q
Viruses account for _____ or more of RTIs.
A
-80% or more
3-4 per year for an adult and 6-8 for children per year
4
Q
Viral respiratory illness stats in children and adults
A
- children: implicated in 40-70% of community-acquired pneumonia; over 90% of bronchiolitis; over 90% of asthma exacerbations
- adults: 30-50% CAP; 80% or more of asthma exacerbations; 20-60% of exacerbations of COPD
5
Q
Those infected with a viral respiratory illness are predisposed to what?
A
-a range of secondary bacterial infections in respiratory tract and can precipitate syndromes affecting other organ systems
6
Q
What is a key feature in acute viral respiratory disease?
A
- seasonality
- incidence highest in winter and lowest in summer
- seen all year round in climates that are not temperate (tropical) and opposite of us in southern hemisphere
7
Q
The location of infection in respiratory tract is related to _______.
A
-various symptoms
8
Q
Systemic vs common local manifestations of acute RTI. How often do these last?
A
- cough, runny nose, sneezing, sore throat, ear pain, congestion
- fever, headache, chills, malaise, myalgia
- 7-10 days at most, 2-3 wks in many, longer in some
- most are acute, mild, and self-limited
9
Q
In general, common respiratory viruses are distributed world-wide, have a short incubation period, and are transmitted _______________. They have similar pathogenesis (describe it) and are associated with increased risk of ____________. Immunity is _________.
A
- person to person
- localized infection and damage to respiratory epithelium
- bacterial superinfection
- imperfect so reinfection is common
10
Q
RV’s are transmitted person to person via ______ and ________ ways. Give examples.
A
- direct and indirect
- direct: direct contact with infected person or aerosolizations of infective droplets during coughing and sneezing
- indirect: hand transfer of contaminated secretions or transfer from contaminated objects to nasal or conjunctival epithelium
- *spreads very quickly**
11
Q
Mechanism of RV infection and establishment and host immune responses to try to fight it off.
A
- virus enters via nose and eyes
- infect ciliated respiratory epithelial cells lining upper and lower airways where they multiply locally without systemic infection!
- cytolytic causing cell damage and eventually death; clearance mechanisms compromised
- Local and circulating antibody release and T cell recognition with release of cytokines and chemokines to recruit neutrophils, NK cells, CD4+ and CD8+ T cells, macrophages, mononuclear cells and eosinophils
12
Q
Certain viruses interact with immune system to promote _____________ lead to virus-induced wheezing and asthma. This immune-mediated injury has been termed ___________.
A
- immediate hypersensitivity
- cytokine storm
13
Q
What is the most common cause of bronchiolitis and pneumonia in infants and children less than 1 year old?
A
- Respiratory Syncytial virus (RSV)
- single most important agent of respiratory disease in infancy
14
Q
What family does RSV below to? Describe the structure of this virus. Is it associated with any unique surface proteins or antigenic types?
A
- paramyxovirus
- enveloped; single stranded (-) RNA
- G and F proteins: G for attachment, F for fusion
- antigenic types A and B
15
Q
Due to RSV’s genomic structure, what must it contain?
A
-RNA-dependent RNA polymerase to turn the -RNA into +RNA
16
Q
RSV was named for it syncytial ability; what protein mediates this?
A
-F protein mediated fusion of cells
17
Q
Source of RSV infection? What is the peak age of contracting this? Why are reinfections common?
A
- humans are the only source of infection; sizeable community outbreaks occur
- virtually all children infected by 2-3 years old with age peak of 2-5 months
- reinfections common for all age groups bc immunity is imperfect and not completely cross protective against the 2 strains–CAN BE REINFECTED IN SAME SEASON
18
Q
What is the only respiratory pathogen capable of causing sizeable outbreaks?
A
-RSV
19
Q
Who goes on to develop very serious RSV illness? What is the mortality in impaired host?
A
- very young infants, especially premature infants
- children 15% in impaired host
20
Q
Of infants <1 y.o. who contract RSV, what percentage die?
A
- 80%
- leading viral cause of mortality in infancy
21
Q
T/F: Most children with RSV infections are previously healthy and therefore, are often asymptomatic.
A
-false, only 0.3% are asymptomatic
22
Q
What is the most classic illness associated with RSV infection in children? Second most classic?
A
- Bronchiolitis
- pneumonia
23
Q
Symptoms of RSV disease in children 1 year and under in URI, LRI, and other areas infection is seen to affect. What do the lungs look like?
A
- URI: cough, rhinitis, pharyngitis, fever
- LRI: expiratory wheezing, air-trapping tachpnea, dyspnea, rales, rhonchi, retractions, nasal flaring, grunting, hypoxemia, irritability, dehydration, and respiratory distress; HYPER EXPANSION OF LUNGS and hypercapnia
- Other: otitis, vomiting, conjunctivitis
24
Q
How long does RSV disease usually last?
A
-10-14 days
25
What is the pathological effect of RSV due to?
-direct viral invasion of respiratory epithelium which is followed by immunologically mediated cell injury
26
What causes the breathing sounds associated with RSV? Compare rales to rhonchi.
- necrosis of the bronchi and bronchioles leads to formation of plugs of mucus, fibrin, and necrotic material within smaller airways which are readily obstructed
- rales: crackling in lower lung due to airways popping throug exudate
- rhonchi: courser sounding and higher up in lungs
27
What are retractions and what do they signify?
- they are inward muscle pulls usually associated with areas near the ribcage
- usually sign of breathing troubles
28
If one were to look at a Chest Xray of a child with RSV bronchitis, what are some key features that one could expect to see? If we took a blood test, would we expect to see RSV in the blood?
- hyperinflation of lungs
- flattened diaphragm with horizontal ribs
- increased hilar bronchial markings
- No; infection localized to respiratory tract and not associated with viremia
29
Adult RSV infections: what are they like? who are they serious in? and what characteristics of patients should be watch out for?
- frequent in healthy adults; mild, influenza-like illness
- serious in elderly and patients with congestive heart failure, bronchipulmonary insufficiency, and immune suppression
- should suspect RSV in all adults who present with fever and pulmonary infiltrates bc it is over overlooked as a cause of death among elderly via pneumonia
30
Grandparents may get RSV from their grandchildren, but where else is a huge concern of contracting this virus? What can help stop this spread?
- hospital!!
- major concern in pediatric wards, nurseries, nursing homes, and adult medical wards
- control spread by careful attention to proper hand washing and infection control guidelines necessary; NO VACCINE!!!
31
Discuss how long RSV can survive on surfaces.
- 3-30 hours on counter tops
- cloth gowns, gloves, tissue for 1 hour
- skin for 30 minutes
32
RSV treatment
- usually supporting and used to maintain hydration and oxygenation, keep airways clear of mucus and debris
- Palivizumab (Synagis): humanized mouse monoclonal antibody for high risk-children
- aerosolized ribavirin for RSV LRTI
33
How is Palivizumab (Synagis) administered? What is it used for? What are issues with aerosolized ribavirin?
- both drugs for RSV
- Synagis: IM injection 1/month during RSV season (usually 5 doses); used to prevent RSV LRTI in selected infants and children
- Ribavirin is a teratogen!!!
34
What family does Parainfluenza virus belong to? Describe their unique proteins and structure.
- Paramyxovirus (with RSV, HMPV, mumps and measles)
- enveloped virus
- nonsegmented, ss RNA genome (-) sense
- envelope has 2 glycoproteins: HN protein with hemagglutinin and neuriminidase activity and F (fusion) protein
35
3 differences between Parainfluenza and Influenza
- Para's RNA synthesis occurs in cytoplasm, not nucleus
- RNA genome is not segments
- hemagglutinin and neuraminidase activity are combined into 1 protein
36
Where does Parainfluenza most typically cause disease?
- larger airways of LRT
| - important cause of LRTI in infants and children
37
Discuss the antigenic types of Parainfluenza and what they differ in.
- 4 serotypes; 1,2,3,4
| - differ in frequency of occurrence, disease spectrum, and epidemic patterns
38
Multiple PIV serotypes and short duration of immunity make reinfection common, but subsequent infections tend to be ____________.
-less severe
39
List 4 common diseases due to PIV, which serotypes causes them, who they mainly cause them in, and what season they occur.
1. Croup: due to virus 1 and 2 (mainly 1); 6-12 months old; autumn
2-3.Bronchiolitis, pneumonia: due to virus 3, infants less than 6 months old, endemic (spring)
4. URI: virus 4; children; endemic
40
How does croup begin? What causes it commonly?
- virus infects epithelial cells of upper airways
- begins as URI with thin nasal discharge, sore throat, mild cough
- within 1-2 d, inspiratory stridor, retractions, worsening barking cough (hoarseness)
41
What is the classic "steeple sign" associated with and what causes it?
- PIV infected xray
| - hoarseness due to narrowing in region of larynx and subglottic trachea
42
Symptoms of croup result from _____________. What is a hallmark of the disease? who does it affect? when does it occur? when does it get worse? how long does it last? how do you treat it?
- inflamed larynx and subglottic airway; may close in severe case
- dry-barking (seal-like) cough is hallmark
- affects children 6mos to 12 y.o. and peaks at 2 years; more common in boys than girls
- most causes occur in fall or early winter
- worsens at night
- self -limited condition lasting 3-7 days, 7-14 days in some
- Tx: if mild disease, supportive therapy; if severe, use O2, nebulized epi, and corticosteroids
43
Describe adenovirus structure and how this influences tropism
- nonenveloped
- icosahedral capsid of hexon and penton capsomers
- dsDNA geomes
- fibers project from capsid at penton base and are major attachment proteins
- penton base and fiber proteins determine serotypes, tissue tropism, and disease
44
Where does adenovirus replication and assembly occur?
-nucleus
45
There are ~______ types of adenovirus and belong to species _________. What species cause what areas of infection?
- 100 (57 infect humans)
- A-G (varied tissue tropism)
- Mainly B and C, some E infect RT
- B and D are ocular
- Primarily F, some A and G cause GI disease
46
Adenoviruses are characterized by their ________________. What percentage of infection result in disease?
- ubiquity and persistence in host tissues
| - 45%
47
Adenovirus epidemiology: be sure to include who is most commonly infected, and how it is spread.
- endemic in US throughout year with sporadic outbreaks with no predictability ***
- epidemics occur in military recruits (4 and 7)
- infections most common in children from 6 mos- 5 years old, but also seen in grade school and junior high school
- spread by respiratory and fecal route via aerosols, fingers, fomites, poorly chlorinated swimming pools
48
Although infections with adenoviruses occur in all age groups, the overall incidence is _________ related to age.
- inversely
| - predilection for infants and children between 6 mos and 5 years of age
49
If you see exudative pharyngitis, what 3 pathogens are you thinking?
- EBV
- GAS
- Adenovirus
50
Why are adenoviruses associated with so many syndromes?
-there are a ton of types of this virus and they have different tropisms
51
Discuss the clinical presentations of adenoviruses you see of the following groups of people: infants and young children, school-aged children, military recruits, transplant recipients/AIDS patients/ other immunocompromised
1. infants, young children: acute febrile pharyngitis, pneumonia, pertussis-like syndrome
2. School-aged children: pharyngoconjunctivial fever
3. military: acute respiratory disease
4. Immunocompromised: disseminated disease (hepatitis, pneumonia), acute hemorrhagic cystitis
52
Adenoviruses and herpes can both cause what eye condition?
-keratoconjunctivitis which can impact the cornea
53
What family of virus does rhinovirus belong to? Genus? Describe its structure and how it attaches to cells
- Picornaviridae family: small ssRNA virus; genus: enterovirus
- naked nucleocapsid with 4 viral proteins VP1-4 that attach to intracellular adhesion molecule-1 (ICAM-1)
54
What is the most commonly identified virus from persons experiencing acute respiratory illness?
-Rhinovirus; affects all age groups
55
How are rhinoviruses organized?
- >100 serotypes/genotypes in 3 groups (A-C)
- 3-4 circulate at a time
* * known for antigenic diversity**
56
What is the common cold virus and what does it attach to on host cells?
- rhino virus
| - ICAM-1
57
What is competitively inhibit of rhinovirus for ICAM-1?
- Zinc
| - hence treatments like Zicam
58
Rhinovirus can cause more serious disease that is completely under appreciated by medical community. Name such issues
- LRTI more common than thought
- can cause significant flu-like illness
- plays major role in significant resp. illnesses like bronchiolitis in infancy, childhood pneumonia, and exacerbate chronic respiratory diseases
59
Characteristics of coronavirus
- enveloped
- positive sense ssRNA
- distint petal or club shaped spikes called solar corona: created by spike protein peplomers
- infects respiratory and GI tracts of mammals and birds
- 4 resp. serotypes
60
Like rhinoviruses, coronaviruses can cause more serious ________.
-LRTI
61
Clinical diseases associated with coronavirus
- 10-30% of common colds
- serious LRTI
- can also cause enteric, hepatic, or neurologic diseases
62
Where can coronavirus be found, aside from humans?
- birds, cats, dogs, pigs, mice, horses, and whales
| - bats
63
What family does Human Metapneumovirus (hMPV) belong to? Describe this virus and morphology.
- paramyxovirus
- found in all age groups
- pleomorphic particles
- ssRNA
- enveloped
- NO hemagglutin
- 2 major groups and 4 genotypes
- most closely related to bird metapneumovirus
64
hMPV epidemiology and disease: what other virus is it similar to clinically? who gets it? what are the clinical presentations?
- similar to RSV
- linked to acute respiratory illnesses in children, elderly, and those with underlying immune compromise and cardiopulmonary disease
- all children infected from 5-10 y.o. but new infections occur throughout life
- range from URI to severe bronchiolitis and pneumonia
65
What are some possible complications of a RVI?
- exacerbation of underlying respiratory disease
- development of chronic lung disease
- possible secondary bacterial infections
- acute otitis media
- apnea, respiratory failure
- SIDS
66
What form of immunity is likely to be pivortal in clearance of RVI's and in recovery?
- cell-mediated immunity
| - illness is milder with reinfections
67
4 common ways to diagnose respiratory viruses
- clinical and epidemiological findings
- viral culture
- rapid antigen detection
- detection of nucleic acids
