Explainer: What should I know about HIV and AIDS?

According to government statistics, someone in the United States becomes infected with HIV every 9.5 minutes. Yet one out of five people with HIV does not know he or she has the virus. That means this person is now at risk of spreading it. So it’s important that everyone knows how it can be picked up, and how it can’t.

HIV, or human immunodeficiency virus, can’t live long outside of people. It can’t be picked up simply by touching or hugging someone who is infected. It can be spread through unsafe sex. It also can be spread through infected blood. In fact, transfusions of blood donated by infected people may be one way the disease got its start in North America. (Blood centers now routinely screen for HIV in donations. They also ask whether blood donors have recently visited countries with high rates of HIV infection.)

In addition, HIV can be passed on from a mother to her child during pregnancy, birth or breastfeeding. HIV can even be spread from an infected adult to a child via pre-chewed baby food. In fact, a 2011 report by the Centers for Disease Control and Prevention, or CDC, found that three in every 10 babies in U.S. households with an HIV-infected mom received at least some pre-chewed food. In most cases, infected moms were doing the pre-chewing.

The CDC recommends that all teens and adults be tested for HIV at least once. That way, they’ll know whether they have been infected.

Why is it so important to know your HIV status? An untreated HIV infection can progress to AIDS, or acquired immune deficiency syndrome. AIDS can seriously damage and ultimately destroy someone’s immune system. This would allow rare infections to take hold and make some cancers much harder to fight.

Doctors have several different ways to tell whether an HIV infection has developed into AIDS. One way is to count the immune system’s surviving T cells. If the number has fallen too low, the person may have AIDS. Doctors also may diagnose AIDS when they find a patient with HIV has acquired one or more certain rare illnesses. Although people with stronger immune systems can easily fight off these types of threats, someone with AIDS cannot.

With medicine, though, even AIDS often can be controlled.

About 2.3 million people around the world became infected with HIV in 2012 (including about 50,000 people in the United States). That’s a lot, but one-third fewer than in 2001.

In 2012, 1.6 million people died from AIDS worldwide. That’s about equal to the entire population of Idaho. But that figure also represents a success: It’s a drop of 30 percent from the 2.3 million AIDS-related deaths seven years earlier.