Initial stages: incubation and primary manifestations
The national classification developed by V.I. Pokrovsky distinguishes several sequential stages in the course of the infection.
Stage 1 (Incubation stage) lasts from the moment of infection to the first immune system response (on average from 3 weeks to 3 months). Symptoms are completely absent, but the virus actively replicates. Specific antibodies are not yet produced — a phenomenon known as the "seronegative window", when diagnosis is only possible via PCR.
Stage 2 (Primary manifestations) reflects the initial immune response. In 50–90% of patients, it presents acutely:
- Stage 2B (acute infection without secondary diseases): often manifests as a mononucleosis-like syndrome (fever, rash, pharyngitis, lymphadenopathy) or neurological disorders (serous meningitis).
- Stage 2C (with secondary diseases): against the background of a transient decrease in CD4+ lymphocytes, mild opportunistic infections such as candidiasis or herpes develop.
Subclinical stage (latent phase)
In 90% of patients, the disease progresses to the subclinical stage (Stage 3). Its core feature is a slow, gradual increase in immunodeficiency. The CD4 lymphocyte count steadily declines at a rate of 50–70 cells/µL per year. The duration of this stage ranges from 2–3 to 20 years (average 6–7 years).
The leading and often only clinical sign of this stage is persistent generalized lymphadenopathy (PGL). Lymph nodes enlarge by more than 1 cm in two or more unrelated groups (excluding inguinal) and persist in this state for at least 3 months. Upon palpation, they are painless and mobile.
Stage of secondary diseases
Continuous viral replication leads to the critical depletion of the immune cell pool, resulting in severe infectious and oncological processes. In clinical practice, the term AIDS is traditionally used to denote late stages (4B and 5).
Evolution of Stage 4 depending on immunodeficiency:
- Stage 4A: CD4 drops to 500–350 cells/µL. Characterized by skin and mucous membrane lesions (recurrent aphthous stomatitis, Herpes zoster, candidiasis). Weight loss is less than 10%.
- Stage 4B: CD4 at 350–200 cells/µL. Weight loss exceeds 10%. Fever and diarrhea lasting more than a month occur. Hairy leukoplakia and localized Kaposi sarcoma are typical.
- Stage 4C: CD4 drops below 200 cells/µL. Cachexia develops, accompanied by generalized infections (cytomegalovirus, extrapulmonary tuberculosis) and CNS involvement (AIDS dementia complex).
Important nuance: changes at stage 4 are reversible. With highly active antiretroviral therapy (HAART), remission can be achieved.
Terminal stage and pathomorphology
Stage 5 (Terminal) is characterized by the irreversible course of secondary diseases. The CD4 lymphocyte count drops below 50 cells/µL. Any therapy becomes ineffective, and death occurs within several months.
The primary target of HIV is the lymphatic system. Macroscopically, this manifests as symmetric adenopathy (cervical, submandibular, axillary nodes). The morphological picture of the lymph nodes goes through three stages:
- Follicular hyperplasia stage: formation of large follicles with high mitotic activity.
- Diffuse hyperplasia stage: erasure of the normal nodal architecture, depletion of follicles, vascularization.
- Lymphoid depletion stage: the node consists only of stroma, lymphoid elements are critically depleted, sinuses are dilated and filled with macrophages.
Briefly: answers to topical questions
Which drug classes are used for highly active antiretroviral therapy (HAART)?
As part of highly active antiretroviral therapy, drugs from the following classes are used:
- Nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs) — analogs of natural nucleosides that terminate viral DNA synthesis.
- Non-nucleoside reverse transcriptase inhibitors (NNRTIs).
- Protease inhibitors (PIs) — block the assembly of new viral particles.
- Viral entry inhibitors — fusion inhibitors (prevent the virus from fusing with the membrane) and chemokine receptor antagonists (CCR5).
- HIV integrase inhibitors — prevent the integration of viral DNA into the host cell genome.
What specific serological methods are used to detect HIV antibodies?
Two main serological methods are used to detect HIV antibodies:
- Enzyme-linked immunosorbent assay (ELISA) — used at the first (screening) stage for the initial detection of the total spectrum of antibodies to HIV-1 and HIV-2.
- Immunoblotting (Western blot) — used at the expert (confirmatory) stage to detail the specificity of detected antibodies to specific viral antigens.
The "IOSVT" stage rule: I — Incubation, O — Acute (primary manifestations), S — Subclinical, V — Secondary diseases, T — Terminal.
Class and exam questions
Why can standard tests yield false-negative results during the incubation period?
During the "seronegative window" period, the virus is already multiplying in the body, but the immune system has not yet produced specific antibodies detectable by standard serological methods.
What is the main cause of death in HIV infection?
Death is not directly caused by the virus itself, but by the development of severe opportunistic infections and malignancies against the background of a destroyed immune system.
How does stage 4 fundamentally differ from stage 5 (terminal)?
The key difference lies in the reversibility of the process: at stage 4, with HAART, transition to a phase of remission is possible, whereas at stage 5, any therapy becomes ineffective.
What else to study on this topic
- Pathomorphology and histological stages of lymph node involvement in HIV
- Classification of HIV infection according to ICD-10 and its logic
- AIDS dementia complex: clinical presentation and CNS involvement
- AIDS-related complex (ARC) and its laboratory markers
- Mononucleosis-like syndrome as a variant of the acute phase of HIV
Master the complete topic in the «Infectious Diseases» course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Clinical presentation and stages of HIV infection" and 3,312 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 41 video lessons on the subject
Other topics in the section "Viral Hepatitis and HIV"
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.