As if waging war against an incurable virus that plagues 34 million people globally weren't enough, researchers, doctors, and public health officials continue to battle yet another elusive problem as World Aids Day approaches Sunday: misinformation.

"It really does obstruct the fight," says Rowena Johnston, vice president and director of research at amfAR, a nonprofit that funds HIV/AIDS research. Broaching topics like sex and drug use­­ -- the major vehicles for transmission -- is "taboo" for many, she says, "so a challenge certainly is getting people to talk openly and honestly about what HIV is and isn't." And part of a candid conversation should be devoted to debunking the myths many have come to believe, including the following:

1. If I had HIV, I would know

Not the case, says Kimberley Hagen, assistant director for the Center for AIDS Research at Emory University in Atlanta. About 1.1 million people in the United States are HIV-positive, and as many as 1 in 5 don't know it, estimates the Centers for Disease Control and Prevention. Many of them feel perfectly healthy. And those who have symptoms may confuse them with run-of-the-mill flu. Denial also plays a role, say experts. "There is a universal tendency with HIV," says Hagen, to try to say, " 'This is something that will affect someone else and not me.' And so you say that you can't get it doing the things that you do -- you can only get it doing the things that other people do. That may be the biggest myth."

2. HIV and AIDS are the same

False: HIV is the virus that leads to AIDS. You could have HIV for years without having AIDS.

3. I don't have to worry because I'm not in a high-risk group

While prostitutes, men who have sex with men, and needle sharers are considered at high risk by the CDC, the virus is an equal-opportunity bug. "Many people don't perceive themselves to be at risk and so don't understand why testing is important," says Joel Gallant, associate director of the AIDS Service at Johns Hopkins Hospital in Baltimore. One example: Heterosexuals account for a third of new HIV transmissions each year, the CDC reports, and a woman might not know her male partner has slept with men in the past or has shared needles with an infected user. Monogamous relationships don't guarantee absolute safety unless you've both been tested and are HIV-negative. In rare instances, women who have sex with women can pass on the virus. And the number of people 50 and older living with HIV/AIDS is on the rise, partly due to newly diagnosed infections, says Paul Weidle, an epidemiologist with the CDC. There are no hallmark characteristics to watch out for, no physical attribute that will "set off an alarm in your head saying 'this person has HIV,' " says Hagen.

4. We're both HIV-positive

We don't need to practice safe sex. Wrong, says Weidle. Superinfection -- where someone gets infected with a different strain of the virus -- is possible. This new strain could be drug-resistant and even stimulate the transition to full-blown AIDS. Not to mention that shunning condoms leaves the body open to other sexually transmitted diseases that an already weakened immune system can't fight off. Birth control also doesn't protect against HIV.

5. HIV transmission by someone on antiretroviral drugs is impossible

While the drugs can lower the amount of virus -- the "viral load" -- in the blood to an undetectable level, it could still register in semen or vaginal fluid and be passed on, says Gallant. Doctors usually test viral load every three to six months, and while chances are "pretty slim" that an undetectable level would suddenly rise, says Gallant, it is possible.

6. I'm sure my doctor has tested me and would have told me if the results were positive

Healthcare professionals will not test you without first talking about it, says Hagen. The CDC recommends at least one test for everyone between the ages of 13 and 64, and those considered high risk should be tested multiple times. Ask your primary-care physician or find a testing center by Zip code here.

7. I won't get HIV through oral sex

Transmission is less common than through anal or vaginal sex, but it is still possible whether performing or receiving oral sex, says Weidle.