4: Viral Causes of Pneumonia

what are the common viral causes of pneumonia
1. influenza types A and B
2. parainfluenza viruses
3. adenovirus
4. respiratory syncitial virus (RSV)
5. cytomegalovirus (CMV)

major risk factors for viral pneumonia
1. age: very young or old
2. immunocompromised individuals at risk: CMV, VZV, HSV, measles, adenoviruses
3. immunosuppression (organ transplant): CMV, RSV

stuff that suggests viral cause of pneumonia
-younger than 5 years old
-ongoing viral epidemic
-slow onset
-rhinitis, wheezing
-low WBC and CRP
-CXR: sole interstitial infiltrates bilat
-slow/nonresponsive response to antibiotics

lab diagnosis of viral pneumonia overview
-slow, expensive!
-antivirals are effective but expensive
-important to d/c antibiotic therapy
-importnat for public health and nosocomial stuff

methodologies of lab diagnosis for viral pneumonia
1. cell culture: cytopathic effect (CPE)
2. shell vial: centrifugation of speciment on cell culture and detectection by flueorescent Ab staining
3. rapid antigen detection
4. PCR (nucleic acid amplification): gold standard

bacterial pneumonia overview of symptoms
-brief duration of symptoms (rapid onset): fever, chills, chest pain, cough
-sputum has PMNs and bacteria
-CXR: reveals focal consolidation (viral is diffuse infiltrates on CXR)

CXR: bacterial vs viral pneumonia
-bacterial: generally see consolidation
-viral: generally see diffuse “ground glass” infiltrates

fungi pneumonia population
-usually only concerned in immunocompromised/suppressed !
(PCP pneumonia= pneumocystis jiroveci)

fungi pneumonia symptoms/signs
-symptoms: slow progression of SOB, fever, nonproductive cough, hypoxemia
-CXR: bilat diffuse infiltrates (or negative cXR)

what to do when suspect PCP pneumonia
-empirically treat until know it is NOT (because can be fatal)
-do it for immunosuppressed/compromised
-treat with Sulfomethoxazole, Pentamidine

buzz words for RSV, influenza, CMV, adenovirus
-RSV: children
-influenza: CXR is variable with diffuse interstitial process, sometimes lobar infiltrates and pleural effusion
-CMV: mostly asymptomatic or mononucleosis syndrome
-adenovirus: contact, crowded living situations

transplant patients CMV complication
PNEUMONIA!

symptoms/signs of CMV pneumonia
(usually transplant pts)
-fever, breathlessness, hypoxemia
-CXR: diffuse infiltrates

how to make diagnosis of viral pneumonia definitive for adenovirus and CMV
-tissue diagnosis by BAL or lung biopsy

adenovirus symptoms/signs
-usually self limiting but aggressive course in immunosuppressed pts (including pneumonia)
-CXR: patchy ground glass infiltrates (primarily in lower lung fields)
-do biopsy
*usually self limited !

transmission of adenovirus
-DNA virus, transmitted by direct contact
-causes 5-10% of febrile illnesses in childhood (most cases asymptomatic)
-some types can establish persistent asymptomatic infections in tonsils, adenoids, and intestines of infected hosts (with shedding)
-disease can result from primary infection (most common), reactivation of infection in pt, reactivation of infection in donor organ

epidemiology of adenovirus
-cause of severe epidemics of acute respiratory disease in military recruits
-80% of recruits get infected, 20% require hospitalization (mainly type 4 and type 7)

immunocompetent hosts adenovirus clinical manifestations
1. asymptomatic
LESS COMMON:
2. pharyngoconjunctivitis (summer camps)
3. hemorrhagic keratoconjunctivitis (medical facilities)
4. acute respiratory diseaes (military recruits)
5. pneumonia

immunocompromised hosts adenovirus clinical manifestations
acute respiratory disease, pneumonia

adenovirus treatment
-in general, d/c any therapy and do supportive therapy!

if pt has pneumonia and is immunocompromised/immunosuppressed what do you treat for until empirically until ruled out?
PCP pneumonia with Sulfa or pentamidine and prednisone (because can be life threatening)

inclusion bodies usually associated with what viral infection
CMV

what is treatment for CMV
-Ganciclovir (anti-viral), good for ACTIVE infection but always have risk for reinfection because there can be latent virus
-it is competitive inhibitor of deoxyguanosine triphosphate

epidemiology of CMV
-CMV infection common (50-80% experienced it) but must asymptomatic

transmission of CMV
-contact with body fluid (blood, saliva, tear, semen) or tissues infected with virus in organ transplant
-establishes latent infection in mononuclear leukocytes and in organs like kidney and heart

2 populations that CMV infection is high risk for illness
1. newborns
2. immunosuppressed individuals (HIV and transplant)

what is THE MOST IMPORTANT respiratory pathogen in infancy and early childhood
-Respiratory Syncytial Virus (RSV)
-confirm with positive ID and r/o bacterial infection

what is necessary for positive diagnosis of severe RSV infections
-nasopharyngeal secretions containing epithelial cells

what are some lab tests to diagnose RSV
-isolate virus
-detect viral antigens
-detect viral RNA
-demonstrate rise in serum Ab
*most labs today use blood tests for antigen detection

RSV treatment
-if mild RSV disease in child, no specific treatment besides symptomatic (Acetaminophen for fever)
-if severe RSV may include nebulized bronchodilators to reverse bronchospasm, O2 therapy, and mechanical ventilation

RSV symptoms
-symptoms: initial runny nose followed by cough and low grade fever, as moves to lower airway illness progress to coughing and wheezing

RSV pathogenesis
-RSV infects respirtory mucosa causing swelling, inflammation of cells of airways fill with fluid
-RSV in respiratory mucosa causes fusion of infected and uninfected cells membranes, then cells die and clump together forming thick mucous…WBC rush to area to fight infection, stimulate mucous production, filling bronchioles with exudate…narrowed swollen airways allow space for intake of air, but prevent it from leaving (air trapping and progressive over-inflation)

RSV epidemiology
-causes MILD respiratory infections in adults
-most common cause of bronchiolitis in infants (most no symptoms, some become very ill)..by year 2, nearly all have had RSV infection

RSV transmission
-highly contagious spread from respiratory secretions through close contact with infected persons
-seasonal…late fall/winter/early spring

immunocompromised pts most at risk for which viral pneumonia
adenovirus and CMV

organ transplant pts most at risk for which viral pneumonia
CMV

neonates and young children most at risk for which infection and pulmonary disease
RSV

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