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Opportunistic Infections

HIV Disease Progression

  • The time it takes from infection of HIV to diagnosis can range from a few months to about 10 years
  • HIV primarily attack and destroy a white blood cell called CD4 or T-lymphocytes. This causes the human body to gradually lose its natural immunity to withstand infections and cancers; which usually holds no threat to a person with an intact immune system.
  • CD4 cells are a part of the immune system and it protects the body by fighting off infections when the body is attack by “intruders” such as viruses and bacteria.
  • Acute infection stage is referred to the initial stage of HIV infection, where large amount of virus are being produced in the body using CD4 cells in this process; hence CD4 count can fall rapidly. During this phase, viral load in the blood can reach 106 copies/ml.
  • The normal range of CD4 cell count is around 500-1500 cell /mm3. When CD4 drops to below 200 cell /mm3 or CD4 is less than 14% of all lymphocytes. The immune system is now weak and it is vulnerable to other illnesses.
  • As the HIV infected person’s immune system deteriorates and cannot fight of opportunistic infections and cancers, this person is regarded as having acquired immunodeficiency syndrome (AIDS).
  • If adults infected with HIV do not receive correct drug treatment, about 50% will present AIDS within 10 years.
  • If children infected with HIV do not receive correct drug treatment, about 40% will present AIDS within 3 years.
  • If CD4 count remains in 50-200 cell/mm3, it is likely that within 18-24 months AIDS patient will develop opportunistic infections and the likelihood of dying is 50-70%.

Opportunistic Infections

HIV primarily destroys CD4 cells/T lymphocytes and causing natural immunity to decrease till it cannot fight off different infections and cancers, that are usually not threats to a person with a good immune system. These infections are called “opportunistic infections”.

There are currently twenty six illnesses used to diagnose AIDS on the HIV surveillance system in Hong Kong. When a person living with HIV suffers from any one of these illnesses they will be classed as AIDS patients. The most common three illnesses for AIDS diagnosis in Hong Kong are: Pneumocystis carinii pneumonia (PCP), tuberculosis (TB) and fungal infections.

Common Opportunistic infections that affects:

  • Respiratory tract: PCP , TB can cause difficulty in breathing
  • Central Nervous system: Toxoplasmosis and cryptococcal meningitis that affects the nervous system
  • Opthamic: Cytomegalovirus retinitis can cause blindness.
  • Gastrointestinal: Cytomegalovirus gastroenteritis/ colitis, cryptosporidiosis can cause bloody stool and ulceration of the esophagus.
  • Skin: Herpes simplex (cold sores, genital herpes ), herpes zoster (chicken pox) and molluscum contagiosum.
  • Affecting Mycobacterium Avium Intracellulare (MAI), Penicillium Marneffei of the body, possibility of fever, anemia,Hepatosplenomegaly etc.
  • Mouth and throat: Candidiasis (fungal infection) causes white spots, ulcers and swallowing difficulties.

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