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Infectious Diseases · Viral Hepatitis and HIV

Viral infections

Infectiones virales

Viral infections represent a vast group of pathologies caused by intracellular genome parasites. They encompass a wide spectrum of diseases ranging from influenza and viral hepatitis to HIV infection, featuring complex mechanisms of systemic damage.

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Nature of pathogensIntracellular genome parasites with high variability
Influenza complicationRefractory hypoxemia and development of viral-bacterial pneumonia
Viral hepatitisMaximum economic burden among infectious pathologies in the Russian Federation
HIV diagnosisTwo-stage laboratory algorithm: ELISA screening and immunoblotting
3 min readFor medical studentsUpdated 10/13/2026
Material prepared by WhiteCoat Pro editorial team based on platform study guidesPending instructor review

Severe course and complications of influenza

The terminal stage of influenza is characterized by a critical drop in blood oxygen levels ($PaO_2$ below 50 mmHg), which is refractory to standard oxygen therapy. The pathogenesis is based on diffuse alveolar damage with the formation of hyaline membranes. Chest radiography reveals bilateral confluent infiltrates radiating from the hila of the lungs.

Non-specific complications are associated with the addition of secondary bacterial flora against the background of the destruction of the respiratory epithelial barrier by the virus. Pneumonias are divided into early viral-bacterial (up to the 4th–5th day of illness, frequently associated with Staphylococcus aureus) and late bacterial, manifesting as a "second wave" of fever during the early convalescence period.

General characteristics of viral hepatitis

The issue of viral hepatitis is relevant due to its colossal global incidence, severe course, and the risk of chronization, which can lead to liver cirrhosis and hepatocellular carcinoma.

Etiological classification distinguishes:

  • True (primary) acute viral hepatitis (AVH): independent nosologies caused by specific hepatotropic viruses A, B, C, D, E.
  • Secondary hepatitis: a syndrome of acute liver injury as a manifestation of other systemic viral infections (herpesviruses, enteroviruses).

The study of hepatitis in a single block is justified by the similarity of their pathogenesis, clinical and laboratory syndromes, and therapeutic approaches.

Test your knowledge on the topicTasks from the "Infectious Diseases" course bank — instant answers and analysis.

HIV infection and principles of its diagnosis

The logical structure of studying HIV infection includes the analysis of the pathogen's taxonomy, its replicative cycle, and tropism for target cells. The disease is characterized by steadily progressive destruction of the immune system and the development of secondary opportunistic infections.

The algorithm of laboratory diagnostics is structured in stages:

  1. Screening: application of enzyme-linked immunosorbent assay (ELISA) to detect antibodies.
  2. Verification: confirmation of the diagnosis by immunoblotting based on the detection of antibodies to specific viral antigens.
  3. Staging: determination of viral load by PCR and quantification of CD4+ T-lymphocytes.

Classification of infectious diseases

The systematization of infectious pathology relies on several key principles:

  • Nosological: classification according to ICD-10 (class A00–B99).
  • Etiological: division into prion, viral, bacterial, fungal, protozoan infections, and helminthiases.
  • Epidemiological: distinguishing exogenous and endogenous infections, as well as anthroponoses, zoonoses, and sapronoses depending on the reservoir.
  • By transmission mechanism: airborne, fecal-oral, vector-borne, contact, and vertical routes.
  • By pathogenicity: division into absolute pathogens with nosological specificity and opportunistic infections.
How to memorize

To remember the two-stage HIV diagnosis, use the rule: Screening (ELISA) → Blotting (confirmation).

Class and exam questions

What are the main pathogens causing viral-bacterial pneumonia in influenza?

Most frequently, viral-bacterial pneumonia in the early stages of influenza is associated with Staphylococcus aureus.

What is the difference between primary and secondary viral hepatitis?

Primary AVH are caused by specific hepatotropic viruses (A, B, C, D, E), while secondary hepatitis is a syndrome or complication of other systemic infections.

What are the main stages of laboratory diagnostics for HIV infection?

Diagnostics includes a screening stage using ELISA to detect antibodies and a verification stage using immunoblotting.

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What else to study on this topic

  • Pathogenesis of the "hyaline membrane" syndrome in severe influenza
  • Clinical features of bacterial post-influenza pneumonia
  • The role of mixed hepatitis (co-infection and superinfection B+D, B+C) in pathomorphosis
  • Spectrum of opportunistic infections in AIDS with CNS and GI tract involvement
  • Quantitative assessment of immune status and determination of viral load in HIV

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Other topics in the section "Viral Hepatitis and HIV"

Etiology and epidemiology of influenzaPathogenesis and clinical presentation of influenzaComplications of influenzaDiagnostics and treatment of influenzaPrevention of influenzaParainfluenzaRespiratory syncytial virus infectionToxic shock syndrome
The entire section "Viral Hepatitis and HIV"

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