An estimated 5.2 million people were receiving life-saving HIV treatment at the end of 2009, according to the latest update from the WHO.
WHO estimates that 1.2 million people started treatment in 2009, bringing the total number of people receiving treatment to 5.2 million, compared to 4 million at the end of 2008.
"This is the largest increase in people accessing treatment in a single year. It is an extremely encouraging development," says Dr Hiroki Nakatani, WHO Assistant Director-General for HIV, Tuberculosis, Malaria and Neglected Tropical Diseases.
At the XVIII International AIDS Conference, WHO is calling for earlier treatment for people with HIV. The objective is to begin HIV treatment before they become ill because of weakened immunity.
"Starting treatment earlier gives us an opportunity to enable people living with HIV to stay healthier and live longer," says Dr Gottfried Hirnschall, WHO Director of HIV/AIDS.
Estimates developed through epidemiological modeling suggest that HIV-related mortality can be reduced by 20% between 2010 and 2015 if these guidelines for early treatment are broadly implemented.
Earlier treatment can prevent opportunistic infections including tuberculosis (TB), the number one killer of people with HIV. Deaths from TB can be reduced by as much as 90%, if people with both HIV and TB start treatment earlier.
The strength of a person's immune system is measured by CD4 cells. A healthy person has a CD4 count of 1000 - 1500 cells/mm3. WHO previously recommended starting HIV treatment when a person's CD4 count drops below 200 cells/mm3 but now advises starting HIV treatment at 350 cells/mm3 or below.
"In addition to saving lives, earlier treatment also has prevention benefits," Dr Hirnschall says. "Because treatment reduces the level of virus in the body, it means HIV-positive people are less likely to pass the virus on to their partners."
WHO's treatment guidelines expand the number of people recommended for HIV treatment from an estimated 10 million to an estimated 15 million. The cost needed for HIV treatment in 2010 will be about US$ 9 billion, according to the Joint United Nations Programme on HIV/AIDS (UNAIDS).
"The investments we make today can not only save millions of lives but millions of dollars tomorrow," said Dr Bernhard Schwartlander, Director, Evidence, Strategy and Results, UNAIDS. "People with weaker immune systems who come late for treatment require more complex and costly drugs and services than those who start treatment earlier and are healthier."
Since 2003 - which marked the launch of the historic "3 by 5" initiative to provide access to HIV treatment to 3 million people living in low- and middle-income countries by the end of 2005 - the number of people receiving HIV treatment has increased 12-fold.
At AIDS 2010, WHO is releasing the 2010 guidelines on Antiretroviral treatment of HIV infection in adults and adolescents - public health approach.