The human immunodeficiency virus is a virus that affects the body’s immune system. For many years it may remain asymptomatic until the moment when the immune system is almost absolutely destroyed and its function is impaired. This advanced stage of the disease is known as AIDS – acquired immunodeficiency syndrome.

To understand better what is HIV and when AIDS may be diagnosed, you should know the characteristics of HIV/AIDS.

What is HIV?

The humaHIV and AIDSn immunodeficiency virus (HIV) is a retrovirus (Retroviridae family) that contains RNA and affects the immune system by attacking CD4+ T-lymphocytes, macrophages and dendritic cells. HIV attaches to the CD 4+ receptors expressed on the surface of these cells and enters their nucleus where with the help of the enzyme reverse transcriptase synthesizes DNA and replicates. Occurs viremia and the HIV spreads throughout the body.

What are the symptoms of HIV infection?

  • Primary HIV infection (Acute HIV infection)

Within 2 to 4 weeks after the HIV contraction develops the condition known as an acute HIV infection. This syndrome is characterized by the various non-specific symptoms – flu-like/mononucleosis-like symptoms (fatigue and general malaise, headache, muscle pain, sore throat, joint pain,  enlargement of the lymph nodes, night sweats, increased body temperature, fever and chills, weight loss, rash, diarrhea, nausea and vomiting etc.). These symptoms may last for a few days or up to four weeks.

  • Chronic HIV infection

For many years (even up to 15 years) HIV infection may remain asymptomatic. The duration of this stage depends on the age of the person and her/his health prior to the infection.

What is AIDS?

The last, advanced stage of HIV infection is known as AIDS – acquired immunodeficiency syndrome.


HIV test

What are the symptoms of AIDS and how is it diagnosed?

A person experiences chronic diarrhea, night sweats, fever, persistent cough, and unintentionally loses weight. The characteristic feature of AIDS is the development of opportunistic infections.

In some cases, HIV/AIDS is only diagnosed when the opportunistic diseases are detected. These diseases are therefore called “AIDS defining” disorders as they are not common for healthy individuals with unaffected immune system.

Such infections include candidiasis, tuberculosis, Kaposi’s sarcoma, cytomegalovirus infection, herpes zoster, histiocytosis, atypical pneumonia and many others.

AIDS is also diagnosed when the CD4+ count is  less than 200 cells/mm3 even when there is no opportunistic infection at the moment.

Feature            HIV     →→→ AIDS
CauseHIV-1, HIV-2HIV-1, HIV-2
Timing May last up to 15 years after the transmissionDevelops after 10 -15 years after the infection was caught
  • Acute retroviral syndrome (flu-like symptoms) that lasts up to four weeks
  • Asymptomatic chronic infection
HIV wasting syndrome and symptoms of opportunistic infections
Opportunistic infectionsNo opportunistic infectionsCandidiasis, tuberculosis, Kaposi’s sarcoma, cytomegalovirus infection, herpes zoster, histiocytosis, pneumocystis pneumonia, toxoplasmosis, cryptosporidiosis, microsporidiosis,

bacterial respiratory diseases, bacterial enteric infections, bartonellosis, syphilis, invasive mycoses, cryptococcosis, coccidioidomycosis, herpes zoster,


CD4+ countMore than 200 cells/mm3Less than 200 cells/mm3 or more if an opportunistic infection is present