HIV (human immunodeficiency virus) was identified in 1983 by the French scientist Luc Montagier and his staff at the Pasteur Institute in Paris. Ever since that discovery, scientists have been searching for ways to treat those infected with HIV, and to produce a vaccine to prevent its spread. While new antiviral treatments have been developed, a vaccine has yet to be found. HIV causes AIDS (acquired immunodeficiency syndrome), an unpredictable condition that may progress over many years and is characterized by a slow deterioration of the . Once an individual becomes infected (HIV has infected the target cells) it takes a week or more before the virus is spread throughout the body's blood and . The immune system responds by turning out HIV in about six to eighteen weeks. The progression of HIV infection to AIDS may take several years. In the initial period, prolonged (2â€“4 weeks) flu-like symptoms may appear. This is followed by an period (clinical latency) that may last ten or more years. When the immune system becomes further compromised, the patient may experience , caused by the reduced function of the immune system resulting in a plethora of nonspecific and variable signs and symptoms. The condition known as AIDS is marked by severe compromise of the immune system and the presence of one or more opportunistic infections. Some clinical signs and symptoms may include sweating, diarrhea, malaise (feeling tired), anorexia (loss of appetite), weight loss, wasting (loss of muscle tissue), chest pain, swelling of the , infections, disorders, body-fat accumulations, and increased blood fats. In addition to disease-induced signs and symptoms, medications used to treat HIV/AIDS may produce additional signs and symptoms.