South Korean students pose in the shape of the Aids ribbon in Cheonggyecheon in 2013 Chung Sung-Jun/Getty Images

World Aids Day, observed annually on 1 December, is dedicated to raising awareness to the Aids pandemic caused by the spread of the HIV infection.

To date, there are an estimated 35.3 million people living with HIV – human immunodeficiency virus. Between 1981 and 2012, Aids - acquired immune deficiency syndrome – has killed 36 million people worldwide.

This year, the theme is Focus, Partner, Achieve: An AIDS-free generation – to highlight the need to for governments and health officials, NGOs and individuals to address Aids prevention and treatment.

Since 1995, the President of the United States has made an official proclamation on World Aids Day. You can watch a livestream of Obama's 2014 White House event here.

History of World Aids Day

The idea for World Aids Day was conceived by two public information officers for the Global Programme on Aids at the World Health Organisation, James Bunn and Thomas Netter, in 1987.

The history of HIV and Aids in the US began in 1981, when the country recognised a new illness among a small number of gay men. Although it widely accepted that the origin of HIV lies in Africa, the US was the first country to bring the virus into the public consciousness.

With the approval of Dr Jonathan Mann, the former head of the Global Programme on Aids (now known as UNAIDS), the decision was made to hold the day on 1 December. It was thought the day would receive maximum coverage by the western media, as it was after the US elections but before the Christmas holidays.

In 1996, UNAIDS took over the planning and promotion of World Aids Day. The White House began marking the day with a display of a 28-foot Aids ribbon in 2007, as the first symbol to hang on the building since the Lincoln administration.

World AIDS Day is observed on social media with the hashtag #WAD2014.

Antiretroviral drugs used for the treatment of HIV Reuters

Facts about HIV/AIDS

Aids is one of the most important global public health issues in recorded history. Caused by infection with HIV, a person may experience a brief period with flu-like symptoms, before a long period with no symptoms. It renders the patient susceptible to infections like tuberculosis and certain cancers.

In the final stages of Aids, lung infections and a type of cancer known as Kaposi's sarcoma are common.

HIV is primarily transmitted via unprotected sexual intercourse, contaminated blood transfusions, hypodermic needles, and from mother to child, via pregnancy, delivery or breastfeeding.

Sub-Saharan Africa remains most severely affected, with nearly one in every 20 adults living with HIV and accounting for nearly 71% of the people living with HIV worldwide.

There are around two million deaths from Aids each year, of which about 270,000 are children.

At the end of 2013, 11.7 million people were receiving ART in low- and middle-income countries, which is around 36% of the 32.6 million people living with HIV in these regions.

Since the beginning of the epidemic, around 78 million people have been infected with the HIV virus.

HIV is treated with antiretrovirals, which work by stopping the virus replicating in the body, allowing the immune system to repair itself and preventing further damage. Patients tend to take three or more types of antiretrovirals – known as combination or antiretroviral therapy.

Antiretroviral therapy prevents the onward transmission of HIV.

Progress has also been made in preventing mother-to-child transmission and keeping mothers alive. In 2013, nearly seven out of 10 pregnant women living with HIV – 970 000 women – received antiretrovirals.