AIDS (Acquired Immune Deficiency Syndrome) is well-known disease related to progressive failure of immune system of its victims. The immune system is a complex organization of white blood cells, antibodies and other proteins. The immune system is able to respond and neutralize foreign bodies from external environment and cancer cells. There is a very important subgroup of white blood cells known as CD4 T-lymphocytes that ensure the proper coordination of immune reactions.


AIDS is an infectious disease, which is caused by HIV virus. The infected person is HIV positive, but that does not mean that this person has AIDS. AIDS should be considered as a complication of long-term negative effect of HIV viral particles. The HIV virus is transmitted by body fluids of the infected individual, typically by blood. However, viral particles also occur in vaginal secretions, semen, saliva and breast milk. The most common modes of transmission are follows:

Unprotected sexual intercourse

AIDS is a typical sexually transmitted disease such as gonorrhea, syphilis, and chlamydia infections. The best prevention is use of condom or non-promiscuous behavior. Anal sex is more risky than vaginal intercourse as the mucous membrane of the rectum gets easily injured and this makes an ideal entry for the virus. In case of unprotected heterosexual intercourse, there is a higher probability that a sick man infects a healthy woman than the other way around. This due to the fact that vaginal mucosa has a large surface, from which the virus may be absorbed into local bloodstream. Mucosal surface of the glans penis in male is much smaller and this decreases risk of infection from a sick woman. Oral sex is also possible way of HIV virus transmission, but the risk is lower than in classic intercourse.

Transmission by a contaminated syringe

The risk of transmission is quite high, but significantly lower than the risk of transmission of infectious hepatitis C. The most threatened groups of people are intravenous drug addicts who share their syringes.

Transmission from mother to fetus

The risk of fetal infection is very high. About 30% of HIV+ pregnant women give birth to a HIV+ child. Aggressive treatment of HIV+ pregnant woman with modern medications can significantly reduce the number of viral particles in blood and the risk of fetal infection is dramatically decreased. After birth, there is also risk of HIV transmission by breastfeeding, because certain amount of viral particles is present in the milk.

Transmission by blood transfusion

This way of transmission has become extremely rare in developed countries in the 21st century.


Note: It is quite clear from the above-mentioned facts that the most risk groups are homosexuals, prostitutes and intravenous drug addicts. High incidence of the disease in homosexual communities in the USA in 1980s was the reason, why AIDS used to be called GRID (Gay-related immune deficiency).


It should be emphasized that the actual infection with HIV and the resulting HIV+ status is not the same thing as AIDS. AIDS usually occurs after a long period of time after the infection. The viral particles attack the CD4 T-lymphocytes and gradually destroy them. As the numbers of CD4 lymphocytes decrease, the immune system deteriorates.  When the number of CD4 lymphocytes falls below 200-500 per microliter of blood, the immunity is seriously dampened and the AIDS occurs. The survival time without treatment is about 10-15 years after the infection.


The infection with HIV has following stages:

First stage: Incubation period

This stage may last for 2-6 weeks after being infected. The virus slowly multiplies, but causes no symptoms. At this stage, the sick person is infectious and can transmit the disease, but the presence of viral particles can not be detected by commonly used blood tests.

Second stage: Flu-like symptoms

This short stage occurs after the incubation period. It manifests with fever, nausea and sometimes with vomiting. Some patients experience an unspecific skin rash and painless enlargement of multiple lymph nodes. The number of CD4 T-lymphocytes drops for the first time, but the immune system is strong enough and the number of lymphocytes rapidly returns to normal. At this stage, antibodies against HIV virus occur in blood and they can be detected to confirm the infection.

Third stage: Asymptomatic stage

This long asymptomatic stage make last for years. The infection slowly spreads and the number of CD 4 lymphocytes gradually drop. When their numbers fall below 200-500 per microliter of blood, the infection may progress into the last stage.

Fourth stage: AIDS

The immune system is significantly weakened and unable to respond to trivial infections. The affected suffer from recurring infections. Even infections that are normally banal have a complicated course and may kill the patient. In addition, the patient suffers from otherwise rare viral and fungal infections. There are also some malignant tumors that frequently occur in patients with AIDS such as the Kaposi’s sarcoma and lymphomas. Very suspicious are recurring yeast infections of skin and mucous membranes (e.g. oral thrush) that do not respond well to therapy.


The modern therapy of HIV infection is surprisingly very successful. There are many special antivirotic drugs that aim to prevent the virus from proliferation. Successful treatment is followed by decrease of viral particles followed with an increase of CD4 T-lymphocytes. Although the disease can not be cured, it can be for a very long time (even for decades) kept in the asymptomatic stage. However, the effective therapy is quite expensive.


When the disease has reached the stage of AIDS and does not respond to antivirotic therapy, the only possible therapy includes cautious treatment of recurring infections.  The prognosis of patients with developed AIDS is nevertheless very poor.


Note: The treatment of pregnant women should be very intensive as it can prevent their child to be born with HIV infection.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources