By Marissa van Hamersveld
Immunosuppression
As discussed before in our article What is the difference between HIV and AIDS?, people with severe suppression of the immune system with CD4 count below 200 cells/ml, are considered to have progressed to AIDS. These people are susceptible to opportunistic infections, which are infections that are more frequent or more severe because of suppression of the immune system. They rarely occur in people with higher CD4 counts or people without HIV or other causes of immunosuppression.
Opportunistic infections
Opportunistic infections in people living with HIV can be caused by bacteria, viruses, fungi and parasites. The following opportunistic infections are observed in people living with HIV:
- Pneumocystis jirovecii pneumonia
Pneumocystis jirovecii pneumonia, formerly called Pneumocystis carinii pneumonia
(PCP), is a severe fungal infection of the lungs. It is possible to prevent and treat
this infection with antibiotics.
- Histoplasmosis
Histoplasmosis is a fungal lung infection. The fungus lives in soil in certain areas contaminated with bat or bird feces, such as Mississippi, Ohio and some parts of the Caribbean, Southern Mexico, Central and South America, Africa and Asia. The risk of getting infected can be reduced by preventing activities involving direct contact with soil.
- Toxoplasma
Toxoplasma is a parasite that usually causes a harmless infection. However, the parasite persists in the body after infection and can therefore be dangerous when the immune system is compromised. In this scenario, the parasite can become active again and cause a life-threatening infection of the brain. Every person with HIV is therefore tested for antibodies against toxoplasma. If no antibodies are detected, meaning the person never had toxoplasmosis infection, preventive measures are recommended to prevent new infection. These include; avoid eating red meat, changing cat litter, and washing hands after gardening.
- Mycobacterium avium complex (MAC)
Mycobacterium avium complex (MAC) is a bacterial infection that causes high fevers, stomach ache and weight loss. It is possible to prevent this infection with antibiotics.
- Candida
Candida is a fungus that can cause infection of the mouth and genitals. This infection happens much more often than the other infections. Preventive medications are usually not recommended.
- Cryptococcus
Cryptococcus is a fungus that lives in soil around bird populations. It can cause severe infections of the lungs or brain, known as cryptococcal meningitis. Preventive medications are not recommended.
- Coccidiodes
Coccioides causes a fungal infection of the lungs, which is called Valley fever. People can become infected by breathing in spores of the fungus, which lives in soil in Arizona and California. Preventive medications are not recommended.
- Cytomegalovirus (CMV)
Cytomegalovirus (CMV) is a virus that also often infects people that do not live with HIV. It usually only causes a mild complaints of fever and muscle aches, but remains in the body after infection. Similar to Toxoplasma, it can become active again in HIV and cause severe infections. Infection of the eyes is the most common and can lead to blindness. Other common infections occur in the gut and brain. Preventive medications are not given, but early start of treatment can prevent further harm.
- Cryptosporidium
Cryptosporidum is a parasite that can cause infection after contact with contaminated water or infected stools, pets or humans. Infection also occurs in people who are not infected with HIV and causes diarrhea. In people living with HIV, the diarrhea is usually more severe and lasts longer. During outbreaks, people living with HIV should avoid contact with contaminated water, infected pets and people.
- Streptococcus pneumoniae
Streptococcus pneumoniae is an infection caused by a bacterium that mostly causes lung infections. Vaccines are recommended to prevent this infection.
- Tuberculosis (TB)
Tuberculosis (TB) is caused by the bacteria Mycobacterium tuberculosis. Infection can involve almost all parts of the body but lung infections are the most common. Some people can also carry a latent infection, which can become active again later in life. In both active and latent infection, treatment is needed. TB is still the leading cause of death among people living with HIV and will therefore be covered in depth in the next article.
Prevention and treatment
The best way to prevent opportunistic infections is to improve your immune system. Therefore, adherence to ART is very important. However, certain infections can be prevented by taking antibacterial or antifungal medications when the CD4 count is low. For the following infections, preventive medication is advised under certain circumstances:
- Pneumocystis pneumonia when CD4 count is under 200 cells/ml.
- Histoplasmosis when CD4 count is under 150 cells/ml, for people who live in areas where histoplasmosis grows (see above).
- Toxoplasmosis when CD4 count is under 100 cells/ml for people who have a positive blood test for Toxoplasma to prevent reactivation of this infection.
- Tuberculosis in case of a positive skin or blood test for tuberculosis.
In most cases, these medications can be discontinued after the immune system has significantly improved for at least 3 months. When infection has already occurred, additional treatment is needed with antibiotics, antivirals or antiparasitics. The kind of treatment depends on the severity of the infection, CD4 count and whether preventive medication was already given. Treatment for these infections is often provided by a doctor specialised in HIV and infectious diseases.
References
Uptodate, Preventing opportunistic infections in HIV (Beyond the Basics), last updated: Nov 16, 2017.
Kovacs et al. Prophylaxis against opportunistic infections in patients with human immunodeficiency virus infection. N Engl J Med 2000.
Panel on Opportunistic Infections in HIV-Infected Adults and Adolescents. Guidelines for the prevention and treatment of opportunistic infections in HIV-infected adults and adolescents: recommendations from the Centers for Disease Control and Prevention, the National Institutes of Health, and the HIV Medical Association of the Infectious Diseases Society of America. http://aidsinfo.nih.gov.ezproxy.leidenuniv.nl:2048/contentfiles/lvguidelines/adult_oi.pdf