Worldwide, about 39 million people are estimated to be living with human immunodeficiency virus (HIV), the virus that causes AIDS — acquired immune deficiency syndrome. And though treatments have kept many carrying the virus alive, the goal is to diagnose HIV before symptoms appear.

One of the biggest challenges to this is that many people don’t know they are infected with HIV, Stacey Rizza, an infectious diseases specialist at the Mayo Clinic, explained. And that means both that the disease can progress to where it is more difficult to treat, and that infected people can unwittingly infect others.

HIV can hide in the body for many years before a person experiences symptoms. Meanwhile, it is killing cells in the immune system, leaving carriers vulnerable to infections and developing cancers.

Researchers used to estimate about 13 percent of those infected with HIV did not know they were infected. That estimate has since dropped to about eight percent, but it is still is not low enough. That is why routine HIV testing is so important, Rizza said in a statement. “We would like to know that everyone who has HIV knows their diagnosis, gets connected to care and starts treatment, so they can protect themselves and reduce their risk of infecting others,” she said.

HIV can hide in the body for many years before a person begins to experience symptoms. Meanwhile, it is killing cells in the immune system called CD4 cells, leaving carriers vulnerable to infections and developing cancers.

HIV is spread through sexual contact, infected needles and contact with the blood of someone who is HIV positive. The virus can also be passed from mother to child, though this mode of transmission is less common.

The best ways to prevent HIV infection continue to be practicing safe sex and not sharing needles. Pre-exposure medications are offered to those at high risk to prevent infection.

There is no cure for HIV/AIDS, but people infected with the virus can now live longer and healthier lives because of better treatments. Anyone who believes they may have been exposed to HIV should see their healthcare provider or go to their local emergency room.

Again, the goal is early treatment — before symptoms appear. “The goal is to diagnose people before they develop full-blown AIDS, to start treatment before the immune system and organs in the body are damaged and they have a chance to infect other people,” said Rizza. If treatment is started early enough, the virus becomes suppressed and the body's CD4 cells return to normal levels.

This is why being tested early is so important. “Every year we see a few more people get functionally cured of HIV, meaning they have gone through some kind of intervention and they no longer need to take the pills,” she explained, “and the virus stays completely suppressed.”