San Diego, California (CNN) -- Antiretroviral drugs that are being used to prolong the lives of patients infected with HIV/AIDS could also be greatly effective in slowing its spread, epidemiologist Brian Williams said.
The concentration of the virus drops by a factor of 10,000 with antiretroviral treatment, resulting in 25 times the reduction of infectiousness, said Williams, formerly of the World Health Organization and now at the South African Centre for Epidemiological Modelling and Analysis. That means that if more people with HIV received this therapy early, there would be fewer new cases of the disease, he said Saturday at the annual meeting of the American Association for the Advancement of Science.
"We could effectively stop transmission within five years," Williams said.
About 33 million people are living with HIV, according to 2008 estimates by the World Health Organization and UNAIDS. That year, 2 million people died of AIDS and 2.7 became newly infected.
Because people who have HIV are living longer, and because in some parts of the world behaviors that facilitate transmission have not decreased, there are more new infections every year than deaths, and the epidemic continues to grow, said Dr. Kenneth Mayer, professor of medicine and community health at Brown University.
In a 2009 article in The Lancet, Williams and his colleagues at the World Health Organization advocated for broader use of antiretroviral drugs, proposing that everyone over age 15 should be tested annually for HIV, and that anyone who tests positive should begin antiretroviral treatment immediately.
These ideas have been gaining support worldwide, Williams said. The National Institute of Allergy and Infectious Diseases plans to start a pilot study in New York and Washington, he said. The International Aid Society is doing something similar in British Columbia, and another trial in South Africa will be funded by the French AIDS Research Agency.
Using antiretroviral drugs early to curb transmission is "an important goal" but will take many years to get right in different settings, Mayer said. Beyond the expanded use of medicine, the details of how to get enough people tested and to change their behaviors is "a whole package that needs to be worked out," he said.
Williams agreed that much operational research still needs to be done to determine if people agree to take the drugs and comply with them, and to see if it leads to the predicted stemming of transmission, Williams said.
Offering testing in communities is one way to get at it, he said. One intervention done in Botswana gave HIV tests to anyone who came to a clinic for any reason, resulting in about one test per person each year.
The proposal is expensive -- the cost in South Africa alone would be $3 billion to $4 billion per year, he said. But the plan would save money from the first day because of all of the people today who have to be hospitalized, and because of all of the young people who die in the prime of their lives, he said.
"If you factor all of the costs, the cost of the drugs would be more than balanced by the cost of treating people for all of these other diseases and then letting them die," he said.
But this should not be seen as an alternative to vaccine research and other activities to curb the pandemic, he said. Toward the end of last year the AIDS research community had a burst of optimism with the results of a controversial trial from Thailand, said Dennis Burton of the Scripps Research Institute. Although the validity of the results is still in question, the news was a "very welcome development," Burton said.
"It's important to realize that the HIV vaccine problem is not one of development," Burton said. There are still many discovery steps that need to be made, and if an effective vaccine could be designed, that would revolutionize the entire study of vaccines for infectious diseases, he said.
In the United States, 20 to 25 percent of Americans living with HIV are unaware of their status, Mayer said. When people are unaware, there are more likely to have unprotected sex and engage in other risky behaviors, increasing the risk of transmission, he said. About 1 million Americans have HIV, he said.
Some people are at high risk for getting AIDS by virtue of where they live, he said. A black male in Washington has about a 1 in 15 or 1 in 16 chance of being infected with HIV, and the probability for a black woman is 1 in 30, Mayer said. This is similar to Detroit, Michigan, and other urban centers. Transmission also is relatively high in gay communities where people who do not engage in risky behavior have risky partners.
"The need [for treatment] will continue to go up over the next few years, and the question is, can we keep up with the pace of the need?" Mayer said.