Respiratory Tract Viruses Flashcards
What is the 4th most common cause of death in US?
-lower respiratory tract
Who is at greatest risk for acute viral respiratory disease?
- the very young
- the elderly
- the chronically ill
- those with immune compromise
- *affects all age groups, but these people more so**
Viruses account for _____ or more of RTIs.
-80% or more
3-4 per year for an adult and 6-8 for children per year
Viral respiratory illness stats in children and adults
- 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
Those infected with a viral respiratory illness are predisposed to what?
-a range of secondary bacterial infections in respiratory tract and can precipitate syndromes affecting other organ systems
What is a key feature in acute viral respiratory disease?
- 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
The location of infection in respiratory tract is related to _______.
-various symptoms
Systemic vs common local manifestations of acute RTI. How often do these last?
- 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
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 _________.
- person to person
- localized infection and damage to respiratory epithelium
- bacterial superinfection
- imperfect so reinfection is common
RV’s are transmitted person to person via ______ and ________ ways. Give examples.
- 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**
Mechanism of RV infection and establishment and host immune responses to try to fight it off.
- 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
Certain viruses interact with immune system to promote _____________ lead to virus-induced wheezing and asthma. This immune-mediated injury has been termed ___________.
- immediate hypersensitivity
- cytokine storm
What is the most common cause of bronchiolitis and pneumonia in infants and children less than 1 year old?
- Respiratory Syncytial virus (RSV)
- single most important agent of respiratory disease in infancy
What family does RSV below to? Describe the structure of this virus. Is it associated with any unique surface proteins or antigenic types?
- paramyxovirus
- enveloped; single stranded (-) RNA
- G and F proteins: G for attachment, F for fusion
- antigenic types A and B
Due to RSV’s genomic structure, what must it contain?
-RNA-dependent RNA polymerase to turn the -RNA into +RNA
RSV was named for it syncytial ability; what protein mediates this?
-F protein mediated fusion of cells
Source of RSV infection? What is the peak age of contracting this? Why are reinfections common?
- 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
What is the only respiratory pathogen capable of causing sizeable outbreaks?
-RSV
Who goes on to develop very serious RSV illness? What is the mortality in impaired host?
- very young infants, especially premature infants
- children 15% in impaired host
Of infants <1 y.o. who contract RSV, what percentage die?
- 80%
- leading viral cause of mortality in infancy
T/F: Most children with RSV infections are previously healthy and therefore, are often asymptomatic.
-false, only 0.3% are asymptomatic
What is the most classic illness associated with RSV infection in children? Second most classic?
- Bronchiolitis
- pneumonia
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?
- 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
How long does RSV disease usually last?
-10-14 days
What is the pathological effect of RSV due to?
-direct viral invasion of respiratory epithelium which is followed by immunologically mediated cell injury
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
