Complications of acute respiratory infections

Pathogenetic mechanisms and main types of complications

Complications of acute respiratory viral infections (ARVI) can develop at any stage of the illness. They are triggered either by the direct cytopathic effect of the viruses themselves or by the superimposition of secondary bacterial flora.

Involvements of the respiratory tract and ENT organs are the most common. These include:

• Otitis media: an inflammatory process in the ear, clinically manifested by constant, shooting, or throbbing pain.
• Sinusitis: involvement of the paranasal sinuses (e.g., frontal sinusitis or maxillary sinusitis).
• Eustachian salpingitis and tonsillitis (angina).
• Bronchitis: can act both as a primary manifestation of viral aggression and as a secondary bacterial complication.
• Pneumonia and bronchopneumonia: severe inflammations of the lung tissue.

At the tissue level, the pathomorphology of complicated forms may manifest as cushion-like proliferations. Moderate cellular infiltration is observed in the pulmonary interstitium, and diapedetic hemorrhages occur in a number of cases.

Specific complications of parainfluenza

Parainfluenza infection is characterized by a specific hierarchy of complications. Lower respiratory tract disorders (bronchiolitis, bronchitis, pneumonia) rank first in frequency, followed by ENT pathologies (otitis media, sinusitis).

Parainfluenza poses a particular danger to young children. The leading and most formidable manifestation in them is acute laryngeal stenosis (obstructive laryngotracheitis).

Neurological disorders are significantly less common: meningitis, neuritis, polyradiculoneuritis, and meningoencephalitis. Non-respiratory pathologies are also possible, such as urinary tract infections, mesenteric lymphadenitis, biliary tract and gastrointestinal tract disorders, and septicopyemia.

Features of respiratory syncytial infection

The causative agent of RSV infection belongs to the family Pneumoviridae (genus Pneumovirus). It is an RNA-containing virus whose natural reservoir is humans and primates. It is transmitted primarily via airborne droplets (less commonly by contact) and possesses pronounced immunosuppressive properties, inducing immunodeficiency. The incubation period ranges from 3 to 6 days. The virus is capable of forming giant cells and syncytia.

RSV infection accounts for 3–16% of all ARVI cases. The incidence exhibits an autumn-winter seasonality, with boys being affected twice as often as girls. Children in the first 6 months of life are in the risk group. Epidemic outbreaks are typical in childcare facilities (especially among toddlers aged 1–2 years), but are also frequently recorded among adults.

The clinical picture and severity of complications directly depend on the patient's age:

• In adults and older children: the virus multiplies in the epithelium of the upper respiratory tract, causing the death of infected cells. The process remains localized to the primary focus and does not spread further; the disease runs a mild or asymptomatic course.
• In infants under 8 months of age: due to the likely absence of secretory immunoglobulin A (IgA) in the mucous membranes of the respiratory tract, the pathogen penetrates into the lower sections and the pulmonary parenchyma. Serous-catarrhal bronchiolitis develops. Inflammatory exudate and sputum containing virions obstruct the bronchioles, which naturally leads to bronchopneumonia.

The prognosis for RSV infection is generally favorable. However, dissemination of the virus via lymphatic and blood vessels is possible in newborns. This can lead to a fatal outcome due to asphyxia (caused by false croup), generalization of the process, or the addition of a secondary infection.

Indications for consultations with allied specialists

If complications are suspected, relevant specialists are invariably engaged in the patient's management to determine further tactics:

• Otolaryngologist: upon clinical signs of otitis media or sinusitis.
• Pulmonologist: upon symptoms of pneumonia.
• Neurologist: in the event of encephalopathy development.
• Cardiologist: upon the onset of acute heart failure or symptoms of myocarditis.
• Hematologist: in hemorrhagic syndrome and marked changes in hematological parameters.
• Obstetrician-gynecologist: if ARVI develops against the background of pregnancy.

Class and exam questions

What else to study on this topic

• Pathomorphological changes in the lungs in ARVI (cushion-like proliferations, diapedetic hemorrhages).
• Epidemiology of RSV infection: seasonality, gender factors, and outbreaks in childcare groups.
• Non-respiratory and neurological complications of parainfluenza.
• Mechanisms of the immunosuppressive action of respiratory syncytial virus.

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.