World AIDS Day 2019: 37.9M people worldwide were living with HIV at the end of 2018

People around the world on Sunday observed the 31st annual World AIDS Day, an event first declared in 1981 aimed at raising awareness of the HIV/AIDS epidemic. It was first declared by the World Health Organization.

According to the Joint United Nations Programme on HIV/AIDS (UNAIDS), 37.9 million people around the world were living with HIV at the end of 2018. UNAIDS reports 1.7 million people worldwide were newly infected in 2018.

The Centers for Disease Control and Prevention reports 1.1 million people were living with HIV in the United States at the end of 2016 and 1 in 7 people nationwide who had the disease didn’t know they were infected.

According to the CDC, “37,832 people received an HIV diagnosis in the United States and dependent areas.”

Worldwide, 770,000 people died from AIDS-related illnesses in 2018, according to UNAIDS. The CDC reports there were 16,350 deaths among people diagnosed with HIV in the United States. The agency added the deaths may be due to any cause.

What do HIV and AIDS stand for?

HIV stands for human immunodeficiency virus. AIDS stands for acquired immunodeficiency syndrome.

What's the difference between HIV and AIDS?

HIV is a virus that can lead to AIDS. AIDS is the last of the three stages of HIV infection.

According to the CDC, people in the first stage, acute HIV infection, experience a flu-like illness within 2 to 4 weeks after infection. It can last a few weeks. People in this stage have large amounts of the virus in their blood, and so are more likely to transmit the infection.

The second stage, clinical latency, marks a period where the virus is active but reproduces only at low levels, HIV.gov says. People in this stage might not experience symptoms but can still transmit HIV to others. This stage can last decades, depending on treatment, but can also be shorter.

AIDS, the third stage, leads to the most severe illnesses because the virus damages the immune system over time, the CDC says. On average, people with AIDS who don't get treatment survive three years, according to the CDC.

Treatment at all three stages can prevent or slow symptoms and reduce the risk of transmission, the CDC says.

How do you know if you have HIV or AIDS?

Testing is the best way to determine whether you have HIV, but symptoms can occur before HIV shows up on a test. Some experience flu-like symptoms – including fever, chills, rash, night sweats, muscle aches, sore throat, fatigue, swollen lymph nodes or mouth ulcers – within two weeks of infection.

How does HIV make you sick?

HIV attacks your immune system by reducing CD4 cells, or T cells, making it harder to fight other infections."Over time, HIV can destroy so many of these cells that the body can’t fight off infections and disease," according to HIV.gov.

According to HIV.gov, the condition becomes AIDS when T cell counts drop below 200 cells per cubic millimeter of blood, or certain AIDS-related complications such as severe infections appear.

How is the virus transmitted?

A person can become infected with HIV only through certain activities in which they come into contact with certain bodily fluids.

Blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids and breast milk can transmit HIV, according to the CDC.

"These fluids must come in contact with a mucous membrane or damaged tissue or be directly injected into the bloodstream (from a needle or syringe) for transmission to occur," the CDC says.

Unprotected anal or vaginal sex with someone who has HIV is one of two main ways the virus is spread in the United States, according to HIV.gov. The use of a contaminated needle or syringe is the other.

A mother may pass the virus on to her child during pregnancy, birth or breastfeeding. It can also be contracted by being struck by an item contaminated with HIV. Other rare but possible ways to spread HIV can be found here.

When did the HIV/AIDS epidemic begin?

U.S. scientists found the first clinical evidence for the disease that would become known as AIDS in 1981, according to the United Nations. Chimpanzees in Central Africa have been identified as the source of HIV in humans. Their version of the virus, called SIV, was likely transmitted to humans and then mutated, the CDC says. HIV has existed in the United States since the mid- to late 1970s.

Can HIV/AIDS be treated?

Yes. People with HIV can take a series of drugs, called antiretroviral therapy, or ART, that slows the virus from progressing, keeps them healthy for years and drastically reduces their likelihood of spreading the virus, the CDC says.

Is there a cure?

Not yet. Researchers are working toward a cure. If a cure were to be found, it'd likely take one of two forms, according to the National Institute of Allergy and Infectious Diseases (NIAID).

Viral eradication would mean HIV was eliminated from a patient's body. The approach would involve "prodding the virus out of its latent state so that an enhanced immune system or administered therapies can target and eliminate HIV-infected cells," the NIAID says. Researchers are also studying gene mutations in certain people whose immune cells resist HIV.

A functional cure, or sustained ART-free remission, would mean that HIV was not eliminated, but rather suppressed to a point at which daily medication would no longer be longer required.

Is there a vaccine?

No, but there have been a number of developments. The National Institutes of Health (NIH) opened the first clinical trial with 138 healthy, HIV-negative volunteers in 1987, according to the NIAID.

In 2016, the NIH announced a vaccine-efficacy trial in South Africa of 5,400 people, the largest in the country's history. Researchers are building on a 2009 success in Thailand, where for the first time ever a vaccine showed modest success in preventing HIV infections.

Should I get tested for HIV?

The CDC recommends everyone from ages 13 to 64 get tested at least once.

People at greater risk of infection, such as sexually active gay or bisexual men, people who have had sex with an HIV-positive partner, people who have shared needles and sex workers, among others should get tested more often.

The CDC recommends testing once a year for people engaging in these higher-risk behaviors. For sexually active gay and bisexual men, the CDC says testing every three to six months is beneficial.

If you are pregnant, and even if you are in a monogamous relationship, the CDC recommends testing to be sure and to reduce the risk of transmitting HIV to your child or partner. The sooner a pregnant woman starts treatment, the less likely she is to transmit HIV to her child.

How do I get tested?

Most HIV tests involve blood or oral fluid. Clinics, hospitals, community health centers and many other locations provide HIV testing. Home testing equipment is also available.

HIV does not always show up right away in a test. Your body and the test type determine how long HIV can take to be detected. Here's a useful guide from the San Francisco AIDS Foundation on testing windows.

For more information on local testing sites, call 1-800-CDC-INFO (1-800-232-4636) or

visit gettested.cdc.gov.

What do the red ribbons signify?

The red ribbon was created in 1991 by artists in New York working to increase awareness of HIV/AIDS. The artists saw the red ribbon as an easy-to-copy way to show compassion for those living with HIV, given the stigma surrounding it.

"They chose red for its boldness, and for its symbolic associations with passion, the heart and love," according to World AIDS Day organizers.

Contributing: Jordan Culver, USA TODAY

This article originally appeared on USA TODAY: World AIDS Day 2019: FAQs about HIV/AIDS in the US and worldwide