Severe course and complications
In severe infections, diffuse alveolar damage develops, leading to refractory hypoxemia. Hemorrhagic pulmonary edema, DIC, and infectious-toxic shock may occur. In the terminal stage, psychomotor agitation increases, and respiratory sounds disappear in the lungs («silent lung»).
Impaired barrier function of the epithelium often leads to secondary bacterial flora (pneumococci, staphylococci, enterobacteria).
Bacterial pneumonia is divided into:
- Viral-bacterial (early): occur up to 4-5 days of illness. Characterized by severe chills, pleural pain, and purulent-bloody sputum. High neutrophilic leukocytosis is present in the blood, while leukopenia is a poor prognostic sign.
- Post-influenza (late): develop during the recovery period, manifesting as a «second wave» of fever and focal changes in the lungs.
In addition to bacterial complications (sinusitis, otitis media, secondary meningitis), autoimmune disorders are possible: myelitis, Guillain-Barré syndrome, as well as rhabdomyolysis with a sharp increase in creatine phosphokinase (CPK), myoglobinuria, and acute renal failure.
Diagnostic methods and differential search
During the epidemic surge, the diagnosis is established based on history and the chronology of syndromes: intoxication appears first, followed by catarrhal symptoms, and from days 2-3 — signs of tracheobronchitis. Outside of epidemics, laboratory confirmation is mandatory:
- Rapid tests: detection of viral antigen in smears by immunofluorescence.
- Molecular genetics: PCR diagnostics of biological fluids.
- Serology (retrospective): CF test and HAI test with paired sera (at the peak of the illness and in 3-4 weeks).
Complete blood count typically shows leukopenia, neutropenia, eosinopenia, and delayed ESR.
In the first 24 hours, the disease is difficult to distinguish from other infections. It is necessary to exclude leptospirosis (calf muscle pain), hemorrhagic fever with renal syndrome (early bleeding, kidney damage), typhus (agitation, enanthema, facial hyperemia), and infectious mononucleosis (tonsillitis, lymphadenopathy, more than 12% atypical mononuclear cells in the blood).
From the second day, with the development of catarrhal syndrome, influenza is differentiated from other ARVI:
- Parainfluenza: laryngitis predominates with hoarseness and a «barking» cough.
- Adenovirus infection: presents with prominent hepatosplenomegaly and lymphadenopathy.
Treatment principles and indications for hospitalization
Patients with mild and uncomplicated moderate influenza are treated on an outpatient basis. The basis of therapy is bed rest, minimization of light and sound stimuli, diet (Table No. 13), and abundant fluid intake up to 2 liters per day.
Symptomatic therapy:
- Antipyretics: prescribed strictly for fever above 38.5°C. The drug of choice is paracetamol.
- Mucolytics: ambroxol, bromhexine, and acetylcysteine stimulate surfactant production. NAC additionally acts as an antidote in paracetamol overdose.
Emergency hospitalization is required for shortness of breath, bloody sputum, hypotension, impaired consciousness, or the onset of seizures. Special attention is paid to risk groups: the elderly, pregnant women, children, and patients with metabolic syndrome.
In the hospital, polyionic solutions for detoxification, forced diuresis, and early administration of donor anti-influenza gamma globulin are used. The development of acute respiratory distress syndrome (ARDS) requires transfer to the ICU for mechanical ventilation, oxygen therapy (target — $SpO_2$ > 90%), and pulse therapy with intravenous glucocorticosteroids (hydrocortisone, methylprednisolone).
Briefly: answers to topical questions
Which direct-acting etiotropic antiviral drugs are used to treat influenza?
For the etiotropic treatment of influenza, direct-acting antiviral drugs are used that block various stages of pathogen replication. These include:
- Oseltamivir — an inhibitor of viral egress from the cell.
- Rimantadine (adamantanes) — an inhibitor of viral release from the endosome.
- Umifenovir — an inhibitor of viral entry into the cell.
- Zanamivir — a neuraminidase inhibitor, also classified as a direct-acting drug.
Class and exam questions
Why are children forbidden to take aspirin for influenza?
The intake of acetylsalicylic acid by patients under 16 years of age against the background of a viral infection highly likely provokes life-threatening Reye's syndrome.
How to distinguish viral-bacterial pneumonia from post-influenza pneumonia?
Viral-bacterial pneumonia develops in the first 4-5 days against the background of intoxication, while post-influenza pneumonia occurs already during the recovery period, manifesting as a «second wave» of fever.
Can an influenza diagnosis be made without laboratory tests?
Yes, but only during an epidemic based on the characteristic clinical picture and epidemiological history. In the inter-epidemic period, the diagnosis is established exclusively by laboratory methods.
What else to study on this topic
- Pathogenesis of infectious-toxic shock and DIC in influenza
- Specific diagnostics of adenovirus infection and parainfluenza
- Features of the clinical picture of leptospirosis and HFRS
- Algorithm for respiratory support in ARDS
- Mechanisms of autoimmune neurological complications (Guillain-Barré syndrome)
Master the complete topic in the «Infectious Diseases» course
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Other topics in the "Respiratory Infections" section
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