HIV Transmission

Researchers have found human immunodeficiency virus (HIV) in virtually every body fluid, including: breast milk, tears, saliva, urine, blood, semen, mucus, vaginal and anal secretions. Despite that, HIV is not casually transmitted from one individual to another. The CDC estimates that in 2006, only 5 new HIV infections were generated by every 100 persons living with HIV.

3 conditions must be met for the transmission of HIV infection:

1. HIV must pass beyond the recipient host's barrier protection, either cutaneous or membraneous.
2. HIV must contact and gain access to a receptive host cell
3. HIV must replicate.

Efficient transmission of HIV is influenced by a number of factors:

Modes of transmission

Viral replication (click here for and interactive diagram of HIV replication)

Infection takes place only when the human immunodeficiency virus (HIV) enters the body and completes a specific set of processes:
1. Binding and fusion: The virus binds with receptors (CD4 and one additional) on the surface of a cell, then fuses with the host cell, inserting its RNA into the host cell.
2. Reverse transcription: An HIV enzyme (reverse transcriptase) uses the single-stranded HIV RNA to assemble a double-stranded HIV DNA molecule.
3. Integration: The HIV DNA enters the host cell's nucleus, where an HIV enzyme (integrase) integrates the HIV DNA into the host cell's own DNA. This now-integrated DNA is called a provirus and may remain inactive for several years, producing few or no new copies of HIV.
4. Transcription: When the host cells receives a signal to activate, the provirus uses a host enzyme called "RNA polymerase" to create copies of the HIV RNA. The RNA is used as a template by host ribosomes to create HIV protein strands.
5. Assembly: An HIV enzyme, called protease, cuts the long chains of HIV proteins at specific sites into smaller individual proteins. These small proteins come together with copies of HIV's RNA genetic material, to create a new viral particle.
6. Budding: The new virus pushes out, or buds, from the host cell. During budding, the new viruses take part of the cell's outer envelope, which acts as a covering, and is studded with protein/sugar combinations, called HIV glycoproteins. These HIV glycoproteins are necessary for the virus to bind CD4 and co-receptors on other host cells. The new copies of HIV can then move on and infect other cells

Symptoms of acute infection

A person who is HIV positive does not automatically have AIDS. AIDS, by definition, is a syndrome with multiple specific symptoms. At least 50% of patients will have symptoms of acute retroviral syndrome within 2-3 months of infection. However, some individuals remain asymptomatic during this period.

Acute Signs
Flu-like symptoms:
  • Fever
  • Myalgia or arthralgia
  • Headache
  • Pharyngitis
  • Nausea and vomiting
  • Fatigue
  • Lymphadenopathy
  • Diarrhea
Rash (Erythematous maculopapular with lesions on face, trunk, and sometimes extremities, including palms and soles; mucocutaneous ulceration of mouth, esophagus, or genitals)
Elevated liver enzymes
Thrombocytopenia, leukopenia
Neurologic symptoms:
  • Meningoencephalitis or aseptic meningitis
  • Peripheral neuropathy or radiculopathy
  • Facial palsy
  • Guillain-Barré syndrome
  • Brachial neuritis
  • Cognitive impairment or psychoses

Criteria for AIDS

A diagnosis of AIDS means that a patient's HIV disease has progressed to include .

  1. CD4 count below 200 cells/mm3 (cubic milliliter) and/or
  2. Development of an "AIDS-defining" condition which includes any of the following:

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