HIV is difficult to treat, but easier to prevent. Here's how to protect yourself.

The Centers for Disease Control and Prevention (CDC) estimates that more than 1 million Americans have human immunodeficiency virus (HIV). Although its prevalence is higher in certain cities, among African Americans, and among men who have sex with other men, anyone can get the disease, which is fatal when not treated. And Americans continue to become infected at high rates, partly due to the widespread belief that you won't get it if you're heterosexual, white, or educated. (In fact, it's believed that one out of every four Americans living with HIV doesn't know he or she has it.)

To reduce your risk, the National Institutes of Health recommends following these guidelines.

Use a condom every time

Seriously, every time—HIV is spread through blood, semen, pre-seminal fluids, vaginal fluids, and rectal fluids, which means that you can contract it through vaginal, oral, and anal sex. Condoms drastically reduce the risk of the virus being spread.

Get tested for HIV

Despite the fact that 45% of Americans have never gotten tested for HIV, the CDC recommends everyone between the ages of 13 and 64 be screened at least once. Those at high risk (such as IV drug users, sex workers, and anyone with an HIV-positive partner) should be tested annually. Testing is free for most people (the Affordable Care Act requires many health insurance plans to offer it without a copay) and you can get results back in just 20 minutes.

Practice safe sex

Before having sex with someone new, ask them about their sexual history. For example, have they ever tested positive for HIV or another STD? How many sex partners have they had in between those tests? Limiting the number of sexual partners you have is another way to decrease your risk.

Don't inject drugs

Because HIV can be spread by blood, sharing a needle with someone who is infected puts you at risk.

Consider a preventative treatment

Those who are at high risk of contracting HIV can reduce their odds by taking a pre-exposure prophylaxis (or PrEP). The PrEP medication Truvada is used to treat HIV and can also help prevent its spread. There are some downsides, however: Truvada is expensive (up to $14,000 a year) and can have life-threatening side effects.