Viral Bronchitis & Pneumonia

What MAJOR viruses are associated with tracheitis (laryngitis) & tracheobronchitis (bronchitis)?
Rhinoviruses (laryngitis & bronchitis), Coronaviruses (laryngitis & bronchitis), Adenoviruses (types 1-7, 14, 21), *Influenzaviruses A and B*, and Human parainfluenza viruses (HPIV 1-4)
What are the two types of bronchitis that are recognized?
1) Short duration bronchitis is associated with the common cold syndrome although of less severity, it is very frequent due to the incidence of common colds
2) Infectious bronchitis (or long duration) on the other hand results in more sever illness, persists after the infection is resolved and is mostly associated with influenza viruses and adenoviruses
What is the epidemiology of laryngitis and bronchitis for influenzaviruses?
The incidence is highly variable. Transmission is primarily through air droplets. The seasonality is according to the etiological agent. The duration is 4 days (rhinoviruses) to several weeks (influenza).
What are common symptoms of tracheitis (laryngitis) and tracheobronchitis (bronchitis)?
Tracheal tenderness, substernal discomfort, non-productive paroxysmal cough (tracheitis and tracheobronchitis). Clear or whitish sputum.

There is a more severe non-productive paroxysmal cough at night in tracheobronchitis, and tracheobronchitis patients also have fever.
How do you diagnose tracheitis (laryngitis) and tracheobronchitis (bronchitis)?
The clinical syndrome and seasonality are the main diagnostic features. Bronchitis is considered as a diagnosis of exclusion, because there are much worse lower respiratory tract diseases.
What is the pathogenesis of tracheitis (laryngitis) and tracheobronchitis (bronchitis)?
Short duration bronchitis is the same as the common cold.

Long duration bronchitis (infectious) - the infection is initiated in the respiratory mucosa. Viral replication progresses along the respiratory epithelium. This leads to a loss and desquamation of respiratory epithelial cells. It is associated with inflammatory cell infiltration. There are direct cytopathic effects, which are believed to be responsible for most of the pathologic changes, but inflammation is also involved.
How do you fight off tracheitis (laryngitis) and tracheobronchitis (bronchitis)?
There are non-specific host defenses including various lectins (mucins in nasal secretions, mannose binding proteins, and surfactant-associated proteins agglutinate the viruses and favor uptake by phagocytic cells), IFNs, Mx protein, and NK cell activity. The CTL response is a major contributor to host defense against influenza viruses. Humoral responses are achieved through IgM, IgG, and IgA antibody production
What are some possible complication of tracheitis (laryngitis) and tracheobronchitis (bronchitis)?
Sinusitis, Otitis-media, Pharyngitis, Asthma, Pneumonia, Croup, Exacerbation of underlying cariopulmonary conditions.
How do you prevent and treat tracheitis (laryngitis) and tracheobronchitis (bronchitis)?
Good hygiene practices, Influenza Vaccination
What viruses primarily cause acute laryngotracheobronchitis (CROUP)?
Parainfluenza viruses (HPIV-1, HPIV-2, and HPIV-3); Influenza A and B viruses, RSV
What is the epidemiology of CROUP?
10-20% of lower respiratory tract diseases of children. Croup is almost exclusively a disease of young children. Transmission through droplets, direct contact, fomites.
What are the common symptoms of CROUP?
Rhinorrhea, sore throat, mild cough, brassy barking cough ("seal's bark"), inspiratory stridor (high pitched sound because of turbulence), fever (except if due to RSV), elevated respiratory rate, chest wall retractions, fluctuating course (condition worsens, improves, worsens within the hour)
How do you diagnose CROUP?
Clinical syndrome and seasonality (not late spring or summer) are sufficient for diagnosis
What is the pathogenesis of CROUP?
Viral infection is initiated in the upper respiratory tract, with inflammation of the nasal passages and nasopharynx, and then moves to the lower respiratory tract.

Most of the symptoms are the result of inflammation and seem proportional to viral replication (in the case of HPIV's at least) in both the upper and lower respiratory tract (epithelium)

Stridor, hoarseness, and cough result from the inflammation of the larynx and trachea, especially at the subglottic level
How do these young children fight off CROUP?
Very limited specific immunity, as re-infections with HPIVs, influenza viruses, and RSV are frequent.

Cellular immunity is thought to be important in viral clearing and avoiding a lethal outcome.
What are some complications of CROUP.
The major one is Otitis media! But also sinusitis and pneumonia.
How do you prevent and treat CROUP?
Good hygiene practices. Vaccination (influenza A and B)
What are the responsible viruses for CROUP?
HPIV-1, HPIV-2, and HPIV-3 (3 out of 4 cases)
Influenza A and B viruses
Classify Influenza A and B viruses
Orthomyxoviridae. Segmented (7-8) (-) ssRNA. Enveloped, spherical. Many types are characterized by their hemagglutinin (15 HA recognized subtypes) and neuraminidase ( 9 recognized NA subtypes). The seasonality is winter to early spring. And it has a wide host range (birds, swine, humans)
Classify Parainfluenza viruses
Paramyxoviridae, (-) ssRNA, enveloped pleomorphic. There are four types (HPIV-1 to HPIV-4); no clinically relevant antigenic strains. The seasonality is from early fall of even-numbered years until 1970 (HPIV-1), early fall of odd-numbered years since 1973 (HPIV-1 and HPIV-2), and late winter-early spring (HPIV-3)
What is the primary cause (virus) of Bronchiolitis?
RSV (Respiratory Syncytial Virus) is the primary virus.

Metapneumoviruses and Parainfluenza viruses also cause bronchiolitis.
Classify RSV.
Paramyxoviridae, (-) ssRNA, Enveloped, pleomorphic, 2 subgroups (A and B) based on the G surface glycoprotein. The seasonality is from mid-winter to early spring.
What is the epidemiology of Bronchiolitis?
It is typically an infection of infants and early childhood (usually children 2 yoa). It's more common in boys. Transmission is through droplets, direct contact (respiratory secretions), fomites. The seasonality is late fall to early spring (rainy season in the tropics)
What are the typical symptoms of bronchiolitis?
Rhinorrhea, cough, expiratory wheezing, air trapping, nasal flaring, subcostal retractions, hypoxia, cyanosis.

Children with underlying cardiopulmonary disease are at risk as well the immunocompromised and premature children.
How do you diagnose bronchiolitis?
The clinical syndrome and the seasonality are the main diagnostic feature.
How do you fight off RSV?
Protection against RSV relies on non-specific and specific host defense mechanisms such as: surfactants, interferons, cell-mediated immunity (CTL), Adaptive immunity (IgM, IgG, IgA)
What are the possible complications of RSV?
Rare: Otitis media

As well as sinusitis, asthma, pneumonia
How do you prevent/treat bronchiolitis?
Good hygiene and Ribavirin for some cases (against RSV)
What are the primary causes of viral pneumonia?
Influenza A and B viruses, Adenoviruses (types 4 and 7 in military recruits) in ADULTS

RSV, HPIVs, Influenza A virus in CHILDREN
What is the epidemiology of viral pneumonia?
It is community acquired. It is transmitted through aerosols, droplets, direct contact, and fomites
What are the typical symptoms of viral pneumonia?
Non-productive cough on onset of disease, scant mucoid sputum to frothy, pink tinged sputum, hypoxemia, cyanosis, increased respiratory rate, dyspnea, rale and wheezing.
What are the three categories within the pathogenesis of viral pneumonia?
1) Infections initiated in and mostly confined to the respiratory tract (influenza RSV)
2) Infections initiated in the respiratory tract that spread systematically (measles and VZV)
3) Systemic infections for which respiratory tract involvement is secondary (CMV)
What is the pathogenesis for influenza specifically as it relates to pneumonia?
The viruses reach the lower respiratory tract when aerosols are inhaled or by contiguous spread from the upper respiratory tract. Infection of the ciliated cells of the respiratory mucosal epithelium of the trachea, bronchi and lower respiratory tract results in the destruction of these cells and tracheitis, bronchitis, and bronchiolitis. Alveolar spaces are infiltrated by neutrophils, mononuclear cells and oedema fluid this disruption of the normal epithelial barrier is favorable to bacterial superinfection
How do we protect ourselves from viral pneumonia?
Protection of the respiratory tract against respiratory viruses and other infectious agents relies on non-specific host defense mechanisms that are:

Anatomic and mechanical barriers, cell-mediated immunity that includes four types of mononuclear phagocytic cells (alveolar macrophages, interstitial macrophages , dendritic cells, and intravascular macrophages), neutrophils, CTL, and NK cells. There is adaptive immunity via bronchus-associated lymphoid tissues and inflammatory mediators
What are the possible complications from pneumonia?
Well you can have a bacterial superinfection (worse form of pneumonia

You can have asthma
How do you prevent and treat pneumonia?
Good hygiene practice and vaccination (influenza, measles, and VZV)