Exam #4: Viral Infections of the Resp. Tract Flashcards
What are the symptoms of the common cold? What symptoms differentiate a cold from a more serious infection?
- Rhinitis (inflammation of the nasal passages)
- Pharyngitis (sore throat)
- Mild cough
Lack of:
- High fever
- Lower respiratory tract involvement
- Dyspnea
What are considered severe respiratory tract infections?
Bronchiolitis
Pneumonia
What complications can be associated with the common cold?
- OM
- Sinus Infections
- Exacerbations of asthma (seen in Rhinovirus C in school age children) & COPD in adults
What viruses are associated with the common cold?
- Rhinovirus*
- Non-SARS Coronavirus
- Adenovirus
- Coxsackievirus
- Influenza B & C vs. A
- Respiratory Syncytical Virus
- Parainfluenza
List the characteristics of the Rhinovirus?
- Picornavirus family member
- Non-enveloped (stable in environment)
- +ssRNA
- Binds ICAM-1 receptor
What are the three types of Rhinovirus?
A, B, & C species
Note also that there are over 100 serotypes; thus, the immune system does generate a memory response, but there the response is serotype specific
How are Rhinoviruses transmitted?
- Shed in respiratory secretions
- Transmission though direct contact with nasal secretions, large droplets, & contaminated fomites
- Extremely low incolum needed for infection
- Incubation period is 1-3 days
Describe the Rhinovirus mechanism of action.
1) Virus attaches to cilia in the respiratory tract via ICAM-1
2) Absorption
3) Replication
4) Replication causes tissue damage & disruption of the epithelial layer= clear fluid out-pouring from the lamina propria
5) Host defenses activated from viral out-poruing & immune system begins to combat the virus
6) Antibody production leads to recovery & epithelium regenerates
How is the Rhinovirus treated?
- Antihistamines
- NSAIDs
- Oral Decongestants
Symptomatic treatment only; NO antibiotics
Characteristics of the Non-SARS coronavirus.
- Coronavirus (named by “corona” appearance under EM”
- Enveloped
- +ssRNA genome
Describe the mechanism of action of the Coronavirus. How is Non-SARS different from SARS?
- Replicate in epithelial cells of respiratory tract
- Optimal temp. for replication is 33-35 degrees C i.e. the cooler upper respiratory tract (vs. SARS that replicate better at body temperature)
How is the coronavirus transmitted?
Large droplets
*Infection more common in infants & children
What is the difference between the long term immune response to coronavirus & rhinovirus?
- Rhinovirus= long term immune response to species
- Coronavirus= no memory response & reinfection to coronavirus can occur despite circulating antibodies
List the characteristics of the Adenovirus.
- Adenovirus
- Non-enveloped
- dsDNA
- Contains adenoviral fiber proteins that are used for attachment & are toxic to cells
Only DNA virus that causes the common cold
Which serotypes of Adenovirus most commonly cause infection of the respiratory tract?
1, 2, & 5
vs. 40 & 41 that more frequently cause gastroenteritis
How is the adenovirus transmitted?
Oral droplets, inhalation, & conjunctiva
How does the pathology of adenovirus differ from rhino & corona?
- May enter lymphoid tissues following acute infection
- Individuals can shed the virus for up to 18 months following infection (asymptomatic)
- No seasonal pattern of disease i.e. patient with cold in the summer is more likely to have adenovirus than Rhinovirus or Coronavirus
What are the other illness associated with Adenoviruses?
- Pharyngoconjunctival fever
- Croup, bronchiolitis, & pneumonia
- GI disease
Which Adenovirus serotypes are associated with GI disease?
40 & 41
To which of the viruses that cause the common cold is a vaccine avaliable?
Adenovirus 4 & 7 (live oral vaccine, given to military recruits)
List the characteristics of the Coxsackievirus.
- Enterovirus, a subfamily of picornovirus (like Rhinovirus) that can pass through the GI tract and remain infectious
- Nonenveloped
- +ssRNA
- survive low pH of GI tract
- Replication is fast & occurs in the cytoplasm
What is the mode of transmission of the Coxsackivirus?
Fecal to oral transmission
What can the Coxsackieirus cause in addition to the common cold?
- Herpangina
- Meningitis or encephalitis (rare)
- Hand-Foot-&-Mouth
What is Herpangina?
- Abrupt onset fever
- Small vesicles on soft palate that rupture & from white ulcers
- More commonly a pediatric disease
What are the symptoms of Hand-Foot-&-Mouth Disease
- Fever
- Vesicular lesions on soles of hand & feet on oral areas
- More commonly a pediatric disease
What is croup? What are the symptoms of croup?
- Acute larygotracheobronchitis ( due to swelling of the subglottic region of the larynx)
- Inspiratory stridor
- “Seal-bark” cough
Note that a prodrome of common cold symptoms precipitates
What is a classic radiographic sign of croup of CXR?
“Steeple Sign”
What should be included in your differential diagnosis of croup?
- FB airway obstruction
- Bacterial epiglotittis (HiB)
How is croup treated? What is the important factor in the diagnostic algorithm?
Does the patient have stridor at rest?
Yes=
1) Oxygen
2) Racemic-Epi
3) Glucocorticoids
No= Humidified Air Hydration
What is croup most commonly caused by? Specifically, what serotype of the virus is associated with acute croup?
Parainfluenza Virus
- Type 1 is the most common cause of acute croup
- Type 2 & 3 can also cause croup, but Type 3 is more commonly associated with lower respiratory tract infections
Also, RSV & Measles can cause croup
List the characteristics of Parainfluenza.
- Paramyxovirus family
- Helical nucleocapsid
- Envelope contains hemagglutinin & neuraminidase–targets for the immune system to recognize the virus
- -ssRNA
- RNA synthesis occurs in the cytoplasm
How is the parainfulenza virus transmitted?
Large droplets & direct contact
Describe the Parainfluenza virus mechanism of action.
Infection & replication in the ciliated epithelium of the respiratory tract
What are the symptoms of influenza?
- Myalgia
- Headache
- Fever/ shaking chills
- Cough peaking between days 3-5
- Fatigue & malaise
How does the flu differ from the common cold?
- Flu generally lasts longer than the common cold
- Increased severity of symptoms
- Pandemic outbreaks
What is a pandemic?
An epidemic of infectious disease that has spread through human populations across a large region; for instance multiple continents, or even worldwide.
What is the definition of pneumonia?
Inflammation of the lung parenchyma leading to abnormal gas exchange
What are the symptoms of pneumonia?
- Fever
- Chills
- Cough
- Pleural chest pain
- Increased respiratory rate
- Wheezes & crackles
- Hypoxia & cyanosis
What virus typically causes primary influenza virus pneumonia?
Influenza Type A
What are the symptoms of primary influenza virus pneumonia?
1-4 days following flu symptoms:
- Increased cough
- Tachypnea
- Dyspnea
- Acute respiratory distress
High Fatality Rate & typically a progressive decline in patient’s status
How is primary influenza virus pneumonia diagnosed?
Sputum Gram Stain
- Abundant PMN cells
- Without significant number of bacteria
CXR
- Bilateral, midlung or lower lung infiltration that is more of an interstitial pattern (like atypical pneumonia) rather than a lobular or typical pneumonia
What is bacterial influenza-associated pneumonia?
Pneumonia that onsets a week after influenza symptoms
What are the symptoms of bacterial influenza-associated pneumonia?
Influenza symptoms that lessen, but are then followed by:
- Increased cough
- Return of fever
- Respiratory distress
“Biphasic”
What bacteria are most commonly associated with bacterial influenza-associated pneumonia?
1) S. pneumoniae
2) S. aureus & H. Influenza
