What Is CD4? Opportunistic Infections (OI) in People With HIV

Many people who have just received an HIV result hear the word "CD4" for the first time and are alarmed by the number on their lab report. I would like you to think of this number as the "fuel gauge" of your immune system. It tells us where you are and what we need to protect against, but it does not tell us what your future will be, because once treatment starts, this number can recover.

What is CD4?

CD4 cells, or CD4 T-helper cells, are a type of white blood cell that acts as the "commander" of the immune system. When germs enter the body, CD4 cells signal other immune cells to deal with them. HIV specifically attacks these cells. Without treatment, the CD4 count falls on average by several dozen cells a year, so the immune system weakens little by little, with no warning symptoms at first.

What does each CD4 level mean?

The CD4 count can vary with illness, stress or even the time of day blood is taken, so doctors look at the trend rather than a single number, and sometimes also at the CD4 percentage (CD4%).

< 100 or 50Very lowRisk of fungal infection of brain and blood

< 200Advanced HIVFormerly called AIDS; high risk of opportunistic infections

200–350Clearly reducedTB and some infections begin to threaten

350–500Starting to fallImmunity beginning to weaken

500–1,500Normal rangeSeen in the general population

Low immunityNormal immunity

Cells/mm³. Doctors look at the trend, not one number, and CD4 can recover once treatment starts.

How is CD4 different from viral load?

• CD4 tells us "how strong the immune system is". It is used to assess the risk of opportunistic infections and decide which preventive medicines are needed.
• Viral load (the amount of virus in the blood) tells us "whether the antiretroviral medicine is working". The goal is undetectable, which is the basis of U=U.

Today, everyone with HIV should start antiretroviral treatment without waiting for the CD4 count to fall. After starting treatment, CD4 usually rises quickly in the first year, then keeps rising gradually in the following years. People who start with a very low CD4 count may take longer to recover. Once the virus is well controlled and the CD4 count is stable and high, WHO guidelines say frequent CD4 testing may no longer be needed, and viral load becomes the main test for follow-up. (Read HIV treatment and the TLD regimen.)

What are opportunistic infections (OI)?

Opportunistic infections (OI) are infections caused by germs that rarely make people with healthy immune systems seriously ill, but that "take the opportunity" to cause severe disease when immunity is low. They are not limited to HIV; they also occur in people receiving chemotherapy, organ transplant recipients and people taking immunosuppressant medicines.

Common OIs in people with HIV in Thailand include:

• Tuberculosis, which can occur at any CD4 level and is a major cause of death. Symptoms include a long-lasting cough, fever, night sweats and weight loss.
• Pneumocystis pneumonia (PCP), usually when CD4 is below 200: increasing breathlessness, dry cough and fever.
• Cryptococcus, a fungus that causes meningitis: severe headache, fever, stiff neck and confusion.
• Talaromyces marneffei, a fungus common in northern Thailand and Southeast Asia: fever, weight loss and skin bumps with a dip in the centre.
• Toxoplasmosis of the brain: headache, seizures and weakness in the arms or legs.
• Candidiasis of the mouth and oesophagus: white patches in the mouth and painful swallowing.
• Cytomegalovirus (CMV), when CD4 is very low, which can inflame the retina, causing blurred vision or floaters.

OI

Lungs

• Tuberculosis (any CD4 level)
• PCP pneumonia (CD4 < 200)

Brain

• Cryptococcal fungal infection
• Toxoplasmosis

Skin and whole body

• Talaromycosis (fungal)
• Fever, weight loss, dimpled skin bumps

Mouth, esophagus, eyes

• Candida fungal infection
• CMV retinitis

The most effective prevention is to test for HIV and start treatment early.

How can OIs be prevented?

1. Test for HIV and start treatment early. This is the most effective prevention of all. (Read HIV self-test if you have never been tested.)
2. Screening before treatment, such as tests for tuberculosis and a blood test for cryptococcal antigen (CrAg) when CD4 is low, so infections can be treated before symptoms appear.
3. Preventive medicines according to CD4 level, such as co-trimoxazole when CD4 is below 200, tuberculosis preventive treatment once active tuberculosis has been ruled out, and antifungal medicine in some cases. When CD4 has recovered above the threshold for several months, the doctor will consider stopping some of them. Do not stop or start them on your own.
4. Vaccines, such as influenza, pneumococcal vaccine, hepatitis B and the HPV vaccine. Some live vaccines should be avoided when CD4 is below 200, so talk to your doctor before vaccination.
5. Food hygiene: eat well-cooked food, wash your hands, and be careful with cat faeces and raw meat when your CD4 count is low.

Symptoms that need urgent medical care

If you have HIV, especially with a low CD4 count or before starting treatment, go to hospital promptly if you have any of these (in an emergency in Thailand, call 1669):

• Unusually severe headache, stiff neck, confusion, seizures, or weakness in the arms or legs
• Increasing breathlessness or feeling you cannot get enough air
• Fever lasting more than 1 week, major weight loss, or a cough lasting more than 2 weeks
• Sudden blurred vision, or many more dark floaters
• Long-lasting diarrhoea, or swallowing so painful you cannot eat

How I can help

At Dr. Kris Clinic in Surat Thani, I explain your CD4 and viral load results, plan screening tests, review the preventive medicines and vaccines that suit each stage, and coordinate referral to the right hospital when needed. If you have just received your result and are worried about the future, read HIV does not have to mean a shorter life and then come and talk with me, at the clinic or online. English-speaking consultations are available.