AIDS :

Acquired Immune Deficiency Syndrome or acquired immunodeficiency syndrome.

Many people with HIV do not know they have it. The number of people with HIV is unknown.

Some of the infections and cancers that people with AIDS get are not common. People who have good immune systems do not get these diseases. Many of these diseases are called AIDS defining illnesses.

In medicine, transmission is the passing of a disease from an infected individual or group to a previously uninfected individual or group. The microorganisms (bacteria and viruses) that cause disease may be transmitted from one person to another by one or more of the following means:

· droplet contact - coughing or sneezing on another person.

· direct physical contact - touching an infected person, including sexual contact.

· indirect contact - usually by touching soil contamination or a contaminated surface.

· airborne transmission - if the microorganism can remain in the air for long periods.

· fecal-oral transmission - usually from contaminated food or water sources
· vector borne transmission - carried by insects or other animals .

A hypodermic needle is a hollow needle commonly used with a syringe to inject substances into the body. They may also be used to take liquid samples from the body, for example taking blood from a vein in venipuncture.

A hypodermic needle is used for instant delivery of a drug, or when the injected substance cannot be ingested, either because it would not be absorbed (as with insulin), or because it would harm the liver (as with testosterone). There are many possible routes for an injection.

The diameter of the needle is indicated by the needle gauge. Various needle lengths are available for any given gauge. There are a number of systems for gauging needles, including the Stubs Needle Gauge, and the French Catheter Scale. Needles in common medical use range from 7 gauge (the largest) to 33 (the smallest) on the Stubs scale. Twenty-one gauge needles are most commonly used for drawing blood. Although reusable needles remain useful for some scientific applications, disposable needles are far more common in medicine.

The twentieth century saw a remarkable shift in the way that vast numbers of people lived, as a result of technological, medical, social, ideological, and political innovation. Arguably more technological advances occurred in any 10 year period following World War I than the sum total of new technological development in any previous century. Terms like ideology, world war, genocide, and nuclear war entered common usage and became an influence on the lives of everyday people. War reached an unprecedented scale and sophistication; in the Second World War (1939-1945) alone, approximately 57 million people died, mainly due to massive advances in weaponry. The trends of mechanization of goods and services and networks of global communication, which began in the 19th century, continued at an ever-increasing pace.

One million (1,000,000), or one thousand thousand, is the natural number following 999,999 and preceding 1,000,001.

In scientific notation, it is written as 106. Physical quantities can also be expressed using the SI prefix mega, when dealing with SI units. For example, 1 megawatt equals 1,000,000 watts.

The million is sometimes used in the English language as a metaphor for a very large number, as in "Never in a million years" and "You're one in a million", or a hyperbole, as in "I've walked a million miles". Hence, a millionaire is a rich person, no matter the actual currency or the exact quantity. Il Milione is the title of Marco Polo's narration of his travel to China. The name is supposed to come from Polo's nickname after his tales of riches and multitudes.

The word "million" is common to the short scale and long scale numbering systems (and also to the proposed Rowlett numbering system), unlike the larger numbers, which have different names in the two systems.

Antiretroviral drugs are medications for the treatment of infection by retroviruses, primarily HIV. Different classes of antiretroviral drugs act at different stages of the HIV life cycle. Combination of several (typically three or four) antiretroviral drugs is known as Highly Active Anti-Retroviral Therapy (HAART).

Organizations such as the National Institutes of Health (Bethesda, Maryland, USA) recommend offering antiretroviral treatment to all patients with HIV-related symptoms. However, because of the complexity of selecting and following a regimen, the severity of the side effects, and the importance of compliance to prevent viral resistance, such organizations emphasize the importance of involving patients in therapy choices and recommend analyzing the risks and the potential benefits to patients without symptoms.

Synergistic enhancers either do not possess antiretroviral properties alone or are inadequate or impractical for monotherapy, but when they are taken concurrently with antiretroviral drugs they enhance the effect of that drug (often by altering the metabolism of the other antiretroviral). These include ritonavir. Ritonavir is per se an antiretroviral drug which belongs to the class of protease inhibitors. It can however be administered at a "baby" dosage to reduce the liver metabolism of other antiretroviral drugs.

Combinations of antiretrovirals create multiple obstacles to HIV replication to keep the number of offspring low and reduce the possibility of a superior mutation. If a mutation arises that conveys resistance to one of the drugs being taken, the other drugs continue to suppress reproduction of that mutation. With rare exceptions, no individual antiretroviral drug has been demonstrated to suppress an HIV infection for long; these agents must be taken in combinations in order to have a lasting effect. As a result the standard of care is to use combinations of antiretroviral drugs. Combinations usually comprise two nucleoside-analogue RTIs and one non-nucleoside-analogue RTI or protease inhibitor.