NEW YORK (FORTUNE) - The U.S. Centers for Disease Control recently recommended that tests for HIV be extended to all patients entering hospitals and clinics, marking a watershed moment in the nation's fight against the virus that causes AIDS.

More than one million Americans are living with HIV and AIDS. And some 25 percent of them are unaware that they have HIV, the virus that causes AIDS.

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The new guidelines, which are aimed at identifying the estimated 250,000 Americans who may be unknowingly spreading HIV, are not only good for the nation's health - they will likely benefit a select group of healthcare companies too.

On the 8th of May, CDC officials said they plan to suggest that doctors begin offering routine voluntary HIV tests to all patients ages 13 to 64. Earlier identification of HIV carriers presents greater opportunity to treat the virus in its early stages, before it progresses into more lethal AIDS.

The new guidelines signal broad change. Coming on the poignant 25th anniversary of the first AIDS cases, the CDC's new tack is an explicit admission that the current approach - testing only people who appeared to be in high-risk categories - is ineffective.

For decades, the federal government's HIV/AIDS prevention campaigns focused on healthy people, offering them strategies for avoiding HIV, such as safe sex via condom use. Where officials once touted prevention by way of abstinence and condom use, they now suggest that Americans keep constant tabs on their HIV status.

"In the early days of the disease, the focus couldn't be on identifying people with the disease because there was so little we could do for them," says Bernard Branson, the CDC's associate director for lab diagnostics in the division of HIV and AIDS prevention.

"People who tested positive would be susceptible to stigma and discrimination without much benefit," he explains, noting that it is now possible for people to live long, healthy lives while treating their HIV.

The CDC is hesitant to predict how widespread testing might affect the spread of HIV. But the center is running computer models to determine just that. "If it becomes normative behavior - knowing the status of your partner before you have sex - then it will be very effective in curbing this epidemic," says Branson.

What gives the federal officials hope are the results of a recent CDC survey, which found that sexually-active adults changed their sexual behavior after being diagnosed with HIV.

According to the poll, wherein researchers asked patients about their sexual behavior in the six months after they discovered their HIV infection, 40 percent say they started using condoms with a sex partner, 27 percent became abstinent, and 15 percent said they were sexually active only with another HIV partner.

The bottom line: "People don't want to incur the guilt of infecting another person," says Branson. So, knowing one's HIV status is key.

The CDC initiative has implications for the healthcare industry. Obviously, the makers of rapid testing devices and HIV medications stand to benefit. The CDC is already a major buyer of the "OraQuick Advance" test kit. Made by OraSure (down $0.09 to $9.22, Research), the oral HIV test is currently the simplest FDA-approved HIV test. Users swab their gums, and wait 20 minutes for an indicator to appear. Much like a pregnancy test, the indicator shows one bar for a negative result and two bars for positive.

The test - used in hopitals and clinics - is under FDA review to be sold as an over-the-counter consumer product. Its closest competitor, Trinity Biotech (up $0.14 to $8.34, Research) sells a rapid blood test.

Although the exact impact isn't yet understood, the market for HIV treatments is likely to expand too - while as many as 250,000 Americans discovery they have the virus. Leading producers of HIV medications, like Abbott Labs (up $0.62 to $42.92, Research), Bristol-Myers (up $0.42 to $24.88, Research), Gilead Sciences (down $0.62 to $56.46, Research), GlaxoSmithKline (up $0.86 to $57.94, Research) are likely to see an uptick in prescription growth in coming years as more Americans begin early HIV treatment.

Currently in the United States, there are four classes of anti-HIV drugs approved for use: nucleoside and nucleotide reverse transcriptase inhibitors (NTRIs), non-nucleoside reverse transcriptase inhibitors (NNTRIs), protease inhibitors (PIs), and fusion inhibitors. In all, those drugs account for roughly $6 billion in annual U.S. sales.