Parainfluenza is an acute viral disease of the upper respiratory tract. Pathognomonic symptoms of the disease are inflammation of the trachea, larynx, the formation of false croup in children. Symptoms of intoxication, fever, nasal congestion, enlarged lymph nodes are also detected. The diagnosis of pathology is based on the detection of the parainfluenza virus in biological materials and antibodies to it in blood plasma. Etiotropic therapy includes antiviral agents, but treatment is mainly symptomatic (antipyretic, expectorant, local vasoconstrictor drugs).
B34.8 Other viral infections of unspecified localization
Parainfluenza is a viral disease transmitted by airborne droplets. The causative agent was identified in 1956 during a study of nasopharyngeal flushes in children with false croup. Currently, five serotypes of the virus have been identified, the first three are distributed around the globe, causing year-round morbidity with a tendency to increase prevalence in the cold season. Parainfluenza accounts for up to 30% of annual ARI cases. The infection is considered one of the most common among preschoolers, who make up 15-50% of the total number of patients. The risk group also includes the elderly, pregnant women, people with immunosuppression, military personnel.
The causative agent of parainfluenza is an RNA-containing virus of the same name belonging to the Paramyxovirus family. Its structure includes hemagglutinin and neuraminidase molecules, an F-protein for the synthesis of new virions. One of the little-studied but proven properties of the virus is the induction of incomplete autophagy in the cells of the immune system, which contributes to the strengthening of extracellular production of parainfluenza virions. The source of infection is a sick person, the transmission path is mainly airborne, less often contact-household. Nosocomial infections often occur in organized children’s groups, as well as among military personnel. In the external environment, the pathogen is unstable, dies when exposed to ultraviolet light, conventional doses of disinfectants, is quickly inactivated when boiling.
After entering the upper respiratory tract through the mouth, nasopharynx, the parainfluenza virus infects the mucociliary epithelium, concentrating on the apical surface of the cells. Due to the high rate of replication of the pathogen, there is a partial fusion of epithelial cells (simplast), hyperproduction of mucus. Local inflammatory reactions are controlled by immune cells, chemoattractants, and the amount of secretory immunoglobulin A synthesized, so the infection spreads beyond the respiratory epithelium of the upper respiratory tract only in weakened and immunocompromised individuals.
Parainfluenza revealed increased formation of interferon-1, 3, involvement of a pool of natural killers, interferon-induced T-cell alpha-chemoattractant, interferon-induced gamma protein. Excessive formation of mucopurulent exudate, accumulation of secretions in the laryngeal lumen, swelling, reflex spasm lead to narrowing of the lumen (false croup). The tropicity of neuraminidase to the nervous tissue causes toxic effects, hemagglutinin causes damage to the vascular wall, although not as pronounced as with influenza.
The incubation period is usually 2-5 days. The height of the disease is preceded by a prodromal period – malaise, weakness, weakness, decreased performance, temperature increase of no more than 38 ° C. Then there is nasal congestion, runny nose with copious mucous discharge, tickling, dryness and sore throat, rough cough, hoarseness of voice. Fever reaches 39° C and above. Hoarseness of the voice occurs and progresses up to aphonia, there are painful sensations behind the sternum when coughing, a slight increase, sensitivity of the submandibular, posterior, rarely axillary lymph nodes.
In the presence of chronic pulmonary pathology, a decrease in the immune reactivity of the body in adults, dangerous signs are increased fever, impaired consciousness, delirium, the appearance of copious sputum, a feeling of lack of air. Prognostically unfavorable symptoms of parainfluenza infection in children are considered to be increasing anxiety, difficulty exhaling, profuse salivation, barking cough, noisy breathing, especially at rest. The appearance of these signs in combination with a forced sitting position with support on the hands, occlusion of the supraclavicular pits, intercostal spaces, cyanotic coloration of the limbs, the tip of the nose, lips is a reason for an emergency call to the doctor.
Late medical treatment, unfavorable premorbid background, pronounced immune suppression lead to a number of complications and life-threatening conditions, especially in childhood. Possible complications from the nasopharynx (sinusitis, tonsillitis, pharyngitis), hearing organ (otitis media, eustachitis), lower respiratory tract (tracheobronchitis, parainfluenza-associated pneumonia). Emergency care is required for false croup, acute respiratory, cardiovascular insufficiency, respiratory distress syndrome. There is a risk of developing meningoencephalitis, generalized parainfluenza infection.
Diagnosis is carried out by an infectious disease specialist, according to indications, consultations of an otorhinolaryngologist, a pulmonologist are prescribed, if a pediatrician is suspected of having a disease. The following laboratory and instrumental methods are used in the process of diagnostic search:
- Physical examination. An objective examination evaluates the level of consciousness, the presence of shortness of breath, cyanosis of the skin. There is hyperemia of the pharynx, difficulty nasal breathing, an increase in the angular, posterior cervical lymph nodes. Diffuse whistling wheezes, dulling of percussion sound from both sides can be heard in the lungs. Laryngoscopy reveals hyperemia, swelling of the laryngeal mucosa, narrowing of the glottis.
- Laboratory tests. A general clinical blood test indicates the presence of leukopenia, monocytosis, acceleration of ESR, less often leukocytosis, neutrophilosis. Biochemical parameters are usually within the normal range, there may be a slight increase in the activity of ALT, AST, CRP. In the general analysis of urine, erythrocyturia, trace amounts of protein are possible. Sputum microscopy is performed for the purpose of differential diagnosis.
- Identification of infectious agents. The PCR technique allows you to isolate the parainfluenza virus from nasopharyngeal flushes, sputum; there are rapid respiratory tests (using immunofluorescence and real-time PCR). ELISA makes it possible to retrospectively establish a diagnosis of parainfluenza, the study is carried out in paired serums at intervals of at least 10-14 days. In the presence of sputum, its bacteriological analysis is required.
- Instrumental diagnostics. When signs of pneumonia appear, chest radiography is prescribed, according to which bilateral lung damage characteristic of this viral infection can be detected. Less often, multispiral computer or magnetic resonance imaging is shown. ECG is performed in the presence of signs of subcompensation of cardiac activity, in patients older than 40 years.
Differential diagnosis is carried out with influenza, other acute respiratory infections, whooping cough, diphtheria, legionellosis, meningococcal infection, measles, pneumocystosis, pulmonary tuberculosis, bacterial bronchitis, pneumonia, bronchial asthma, phlegmonous laryngitis, chondroperichondritis of the larynx, lymphogranulomatosis, congestive heart failure, COPD, Quincke’s edema, malignant neoplasms, foreign laryngeal bodies.
Treatment is usually carried out on an outpatient basis, hospitalization is carried out according to clinical and epidemiological indications. The patient is provided with bed rest until a steady decrease in body temperature to normal figures for 2-3 days, fractional nutrition with the exception of hard-to-digest food, copious drinking, voice mode with the minimization of colloquial speech, adequate microclimate of the room with a comfortable temperature, humidity. Smoking cessation is important both for the patients themselves and for those around them. In case of decompensation of the respiratory system, immediate resuscitation is necessary.
Treatment is symptomatic. Antipyretics (except acetylsalicylic acid and analogues), expectorants (acetylcysteine), antitussive drugs (butamirate dihydrocitrate, guaifenesin), nasal sprays, drops (xylometazoline, phenylephrine, oxymetazoline), solutions for rinsing the throat (chlorhexidine, furacilin) are widely used. If indicated, inhalation or systemic injection glucocorticosteroids, sedatives, bronchodilating, antibacterial agents are used.
Ribavirin and human immunoglobulin have been used in patients with immunosuppression, the proven effect of the use of these medications on reducing the number of complications and deaths has not been described. There are reports of the effectiveness of the drug DAS181, the mechanism of action of which is the selective cleavage of sialic acids of the host cell necessary for the attachment of the virus. The effectiveness of trypanosomacid agents, zanamivir, and some experimental neuraminidase and hemagglutinin inhibitors is being studied in animals.
Prognosis and prevention
The prognosis for uncomplicated forms of the disease is favorable, the phenomena of asthenia, cough can persist up to 2 weeks. The duration of parainfluenza from the first clinical symptoms to the moment of recovery is usually 7-10 days; false croup syndrome occurs in 20-30% of children under the age of 3 years. Repeated cases of parainfluenza have been described 7-9 months after the infection. The development of preventive vaccines has been underway since the 60s of the twentieth century, but there are no licensed drugs.
In experiments on volunteers, live attenuated as well as vaccines containing elements of the cow parainfluenza virus were effective, but recombinant vaccines are most likely to appear. Non-specific preventive measures consist in the identification, isolation, treatment of patients, current sanitary and hygienic treatment, ventilation of premises, avoidance of mass events in the epidemic season, wearing masks, proper nutrition, sleep, hardening of the body.