2. What  are opportunistic  infections? and give examples

Opportunistic infections are infections that occur more frequently and are more severe in individuals with weakened immune systems, including individuals with HIV/AIDS, certain cancer patients, and transplant recipients who are taking certain immunosuppressive drugs.

The pathogens that cause these infections are typically not able to cause disease in individuals with healthy immune systems. However, when the immune system is weakened or suppressed, these "opportunistic" pathogens can cause significant illness.

Examples of opportunistic infections include:

1. Pneumocystis pneumonia (PCP): This is a fungal infection that can cause severe pneumonia in people with weakened immune systems, such as those with HIV/AIDS.

2. Cryptosporidiosis: This is a parasitic infection that can cause severe diarrhea in people with weakened immune systems.

3. Cytomegalovirus (CMV): This is a viral infection that can cause a variety of symptoms, including fever, fatigue, and more serious complications in people with weakened immune systems.

4. Toxoplasmosis: This is a parasitic infection that can cause flu-like symptoms and serious complications in people with weakened immune systems.

5. Candidiasis: This is a fungal infection that can cause a variety of symptoms, including oral thrush and vaginal yeast infections in people with weakened immune systems.