Definition

Opportunistic infections resulting from immunodeficiency conditions are infections caused by organisms that typically do not cause disease. In other words, opportunistic infections occur in individuals with a weakened immune system or immunodeficiency.

Causes

The causes of opportunistic infections commonly include:

• Candida fungal infections, known as candidiasis, can affect the body's skin, nails, and mucous membranes. Individuals with immunodeficiency often experience candidiasis infections, especially in the mouth and vagina. However, candidiasis is considered an opportunistic infection only when it causes severe or persistent infections in areas such as the mouth, vagina, esophagus, lower respiratory tract (such as the trachea and bronchi), or deeper lung tissues.
• Invasive cervical cancer originates from the cervix (the neck of the uterus) and spreads invasively to other parts of the body.
• Coccidioidomycosis caused by the fungus Coccidioides, also known as valley fever, desert fever, or San Joaquin Valley fever. Infection typically occurs through inhalation of fungal spores and is most common in hot and dry areas.
• Cryptococcosis is caused by the fungus Cryptococcus neoformans. It usually enters the body through the lungs and can cause lung infections (pneumonia) and central nervous system involvement (brain and spinal cord), among other manifestations.
• Cytomegalovirus (CMV) can infect various parts of the body and cause inflammation in the lungs, gastrointestinal tract (especially abdominal pain caused by infections in the large intestine), brain, and retina, threatening vision.
• Cryptosporidiosis, a diarrheal disease caused by the parasite Cryptosporidium, presents symptoms such as stomach cramps and severe and chronic watery diarrhea.
• Herpes simplex virus (HSV) infections generally do not cause serious problems for most people. The infection is usually acquired through sexual contact or transmitted from mother to child during childbirth. In individuals with a healthy immune system, HSV typically remains inactive. However, stress, trauma, other infections, or a weakened immune system can reactivate the virus, leading to symptoms. HSV can cause painful cold sores around the mouth, genital area, or anus. In individuals with severely weakened immune systems, HSV can also lead to bronchi (airways), lungs, and esophagus infections.
• Histoplasmosis, caused by the fungus Histoplasma, commonly affects the lungs and presents with flu-like symptoms or pneumonia. Histoplasmosis can persist and spread to other body parts in individuals with severely weakened immune systems.
• Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis. It spreads through the air and can lead to lung infections.
• Toxoplasmosis is caused by the parasite Toxoplasma gondii, carried by cats, rodents, and birds and excreted through their feces. People can become infected by inhaling dust or consuming food contaminated with the parasite. Toxoplasma can also be present in commercial meat, especially red meat and pork, although rarely in poultry. Infection can occur in various organs, including the lungs, retina of the eye, heart, pancreas, liver, large intestine, testes, and brain.
• Mycobacterium avium complex (MAC) infections, caused by several types of mycobacteria found in the environment. These infections can be life-threatening in individuals with weakened immune systems.
• Pneumocystis pneumonia (PCP), a lung infection caused by the fungus Pneumocystis jirovecii, occurs in people with weakened immune systems.
• Other opportunistic infections may include Salmonella infections, sexually transmitted infections, Kaposi sarcoma, and lymphoma.

Read more: Herpes Simplex - Definition, Causes, Symptoms, and Management

Risk Factors

Risk factors for opportunistic infections include:

• HIV/AIDS patients. In developed countries, the number of opportunistic infections in people with HIV has decreased compared to previous years due to the widespread use of HIV medications.
• History of cancer.
• Immunosuppressive drug therapy or long-term corticosteroid use.
• Primary immunodeficiencies, such as severe combined immunodeficiency or selective IgA deficiency.

Symptoms

Because there are many opportunistic infections, signs and symptoms can vary greatly. However, some common symptoms may include:

• Fever
• Headache
• Night sweats or chills
• Joint pain
• Loss of appetite
• Unexplained weight loss
• Enlarged lymph nodes
• Swelling in various parts of the body

Diagnosis

The diagnosis of opportunistic infections is based on several factors, including:

• Medical history and physical examination
• Blood test results
• Culture and sensitivity tests to determine the causative organism

Management

The management will depend on the type of infection but may include:

• Antibiotics (such as azithromycin or clarithromycin)
• Antifungals (such as fluconazole or voriconazole)
• Antivirals (such as acyclovir or valacyclovir)
• Antiretroviral therapy to reduce opportunistic infections associated with AIDS
• Prophylactic antibiotics

Read more: Acyclovir - How it works, Contraindication and Drug interaction

Complications

Untreated opportunistic infections can spread throughout the body and cause organ damage that can be life-threatening.

Prevention

Preventing opportunistic infections primarily involves adopting a healthy lifestyle, which includes:

• Avoiding contact with organisms that can cause opportunistic infections. These organisms can spread through bodily fluids or feces. To prevent sexually transmitted diseases (STDs), use condoms consistently during sexual intercourse. If you inject drugs, avoid sharing injection equipment. Always wash your hands thoroughly with warm water and soap after contact with human or animal feces.
• Being cautious when selecting food and drinks. Food and water can be contaminated by organisms, causing opportunistic infections. Avoid consuming certain foods such as undercooked eggs, unpasteurized dairy products or juices, and raw or sprouted seeds to minimize risks. Cook all raw red meat to a minimum core temperature of 64 degrees Celsius after freezing it for at least 24 hours. Additionally, refrain from drinking water directly from lakes or rivers.
• Adhering to the treatment regimen prescribed by the doctor. For instance, if diagnosed with HIV, regularly take the prescribed medication to prevent damage to the immune system and reduce the risk of opportunistic infections.
• Traveling safely. Before traveling abroad, research information about the destination or consult with a healthcare provider. Avoid consuming food or water that may cause illness, such as tap water.
• Receiving recommended immunizations or vaccinations.
• Maintaining a balanced and nutritious diet.
• Limiting contact with sick individuals.

When to see a doctor?

If you've been diagnosed with immunodeficiency, having regular check-ups with your doctor is important. If you experience any new symptoms, especially those related to infections, promptly consult your doctor for evaluation and early management.

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