HIV is a virus, and like all viruses it is not a true cell, but a microscopic particle much smaller than a bacterium. Viruses are essentially minute 'boxes' made of proteins containing the genetic material that carries the information needed to make more viruses of the same type. But viruses cannot reproduce themselves unless they invade a true cell and take control of the normal chemical processes taking place in the cell. The virus turns the cell into a virus 'factory', producing millions of new viruses and killing the host cell as it sheds its load of viruses into the body.
There are different types of viruses, and HIV belongs to a group called the retroviruses. This name is important because the drugs that have been developed in recent years to treat PLHIV are called antiretrovirals (or ARVs), and the combination of drugs and other treatments that an individual receives is called antiretroviral therapy (or ART). You will learn all about ARVs and ART in Study Sessions 22 and 23.
There are two species of HIV, known as HIV-1 and HIV-2. HIV-1 is the virus responsible for the majority of HIV infections in most countries, including Ethiopia. HIV-1 is more infectious and has a much greater ability to be transmitted between people than HIV-2. (HIV transmission will be discussed in more detail in Section 20.4.) HIV-2 infection is mainly prevalent in West African countries, and it is thought to induce progression to HIV-associated diseases and AIDS more slowly than HIV-1.