AIDS overview and Definition

A disease of the immune system caused by HIV(human immuno deficiency virus).AIDS is the late stage of HIV infection.


Prevalence of HIV is approx. 37 million worldwide. Approx. age for peak incidence of HIV is 20-40 years. However, the advanced stage of the disease known as AIDS is seen more predominantly in people in their 4th decade.

Structure of AIDS

The shape of the virus is spherical.The virus is composed of a capsid core which contains the genetic materials and it it has a protein envelope.This protein envelope has many glycoprotein (gp 120,gp 41).The envelope of the HIV also contais other proteins including some HLA (human leucocyte antigen).The genetic material of this virus contains two helices of RNA molecule in folded form.The enzyme REVERSE TRANSCRIPTASE aids the virus in the conversion of RNA to DNA in host cell.The enzyme INTEGRASE helps the viral genome to be incorporated in the host cel.

Routes of Transmission

Sexual  Transmission:

About 80% of infections worldwide are transmitted through sexual transmission. The risk of transmission depends on various factors including - sexual partner's viral load, the type of sexual exposure, coinfection with other conditions like HPV, and genital inflammation or damage.

  1.  Parenteral transmission:
      • Needle Sharing
      • Needle stick injuries
      • Infectious blood on mucous membrane
      • Blood transfusions
  2. Vertical transmission

When the virus spreads from mother to child during When the virus spreads from mother to child during pregnancy, childbirth or during breast feeding, it is called as vertical transmission. The Risk of transmission can be lowered significantly if HIV infection is treated consistently and viral load is maintained below the limit of detection.

Clinical signs & symptoms


In early HIV infection, the patients are generally asymptomatic. The viral incubation period is about 2-4 weeks, after which they may present with flu-like symptoms of acute infection for a period of 2-4 weeks.  The infectiousness occurs in two peaks. The first peak occurs within the first few months after infection. The second peak occurs during the AIDS stage. In Acute HIV infection, also called as Acute Retroviral Syndrome (ARS), the patients present with the following non-specific flu like symptoms -

  • Fever
  • chills
  • Fatigue
  • Myalgia and arthralgia
  • Night sweats
  • Headache
  • Generalized non-tender lymphadenopathy 
  • Gastrointestinal symptoms (nausea, diarrhea, weight loss)
  • Oropharyngeal symptoms (sore throat, ulcerations, painful swallowing)


In chronic HIV infection, the patients are asymptomatic and it lasts for a period of 2-10 years. The HIV Viral load increases in the blood and the immune cell count (T-cell, CD4+ cell) decreases.

Differential Diagnosis

The presence of HIV in the body can be detected by testing for HIV virus (viral antigen) and HIV antibody (chemicals produced in the blood to fight HIV) in the blood of the suspected patient. Also, the CD4+ T-cell count in the blood is tested to diagnose HIV. The various diagnostic tests for HIV and AIDS consist of the following:

  1. SCREENING TESTS (detects HIV antigen and  anti-HIV antibodies  in the blood)
    1. Combination antigen/antibody tests -
      1. detects both HIV antigen (p24) and anti-HIV antibodies

      2. 4th Generation HIV test

    2. Antibody only tests (HIV serology)

      1. ELISA (enzyme-linked immunosorbent assay)

      2. Rapid tests

  2. CONFIRMATORY TESTS (detects anti-HIV antibodies in the blood)
    1. HIV-1/HIV-2 antibody differentiation immunoassay
      1. First choice of confirmatory test

      2. can detect both HIV-1 and HIV-2 in ∼ 20 minutes and distinguish between the two types

    2. Western blot
      1. tests may be negative up to 2 months after infection

      2. results are usually available after several days


This test can detect HIV infection earlier than antibody/antigen-based tests (within 10-33 days of exposure).


  • Untreated HIV infection has a mortality rate of > 90%

  • The prognosis depends  upon various factors

  • Adequate retroviral treatment

  • Viral load at the beginning of the clinical stage of HIV infection

  • CD4 count over the course of the disease

  • Preexisting conditions

  • Presence/ absence of opportunistic infections

  • Individual genetic properties

  • HIV species and subtype.


  • Screening of blood before Transfusion

  • Screening of blood for pregnancy women.

  • Avoid sharing needles

  • Use Sterilization protocol whenever it is needed.

  • Avoid sharing of razor blades or toothbrushes.

  • Follow safe sexual practices

  • Tell your sexual partners that you have HIV.

  • Take preexposure prophylaxis(intake of antiretroviral drugs) when your partner is HIV positive.

  • In cases of  injury with HIV-contaminated instruments or needles , unprotected sex or contact of open wounds with HIV contaminated fluids, a HIV post-exposure prophylaxis should be initiated as soon as possible (ideally with 3 hours after exposure).