While children and teens tend to need more sleep than adults, constant or chronic sleepiness could be a sign of a physical or psychological problem. Constant fatigue can effect a child's school work and social life.

Since human immunodeficiency virus, or HIV, appeared in the mid-1980s, many nations have refused visitors who have HIV. Even the United States has had a ban on HIV-infected travelers, although that may be lifted.

The human immunodeficiency virus, which is transmitted via unprotected sex and contaminated blood, weakens the immune system and eventually leads to acquired immunodeficiency syndrome. Because of the weakened immune system, the body is unable to fight off infection.

Fatigue is best described as a lack of energy, tiredness or weariness, according to MedlinePlus. Fatigue can result from taking certain medications or from underlying medical conditions.

C-ANCA and p-ANCA are two tests used in the diagnosis and evaluation of rheumatologic diseases. These conditions often result from a dysfunction in the immune system, which triggers an attack on certain tissues in the body that it mistakes as foreign or invading microorganisms or poisons.

Everyone is born with an immune system. It consists of a team of cells, proteins, tissues and organs that fight off illness, germs and other invaders. When an unsafe substance enters the body, the immune system kicks into gear and attacks. In a baby's first few months, her immune system is not fully developed.

The urinary system is comprised of the kidneys, ureters and bladder as well as sphincter muscles and the urethra.

Exhaustion—also referred to as extreme fatigue—is a severe lack of energy that affects a person’s ability to perform mental or physical tasks. While the possible causes of exhaustion are virtually endless, the most common include excessive stress and lack of quality sleep.

Acute HIV refers to the 6-to-12-week period when HIV infection first occurs. It is during this time that HIV antibodies develop, creating the virus that attacks the immune system. Over time and without treatment, HIV can lead to AIDS.

When a patient is infected with the human immunodeficiency virus, or HIV, there are some symptoms that can identify the infection early. The initial stage of HIV, according to National Health Services UK, is called primary infection.

Antibodies are critical to your immune system's function. These cells are present in the body to ward off illnesses, including viruses and bacteria, and the more you have, generally, the healthier you will be.

Suffering from chronic inflammation can lead to all kinds of problems in your body. Vitamin C is a water-soluble vitamin that plays a role in protecting joints, boosting your immune system and relieving inflammation. Your body absorbs and uses vitamin C immediately and excretes any excess.