Being infected with human immunodeficiency virus (HIV) is no longer a death sentence, as medication can control the virus and lower the risk of transmission.
But a Singaporean expert says a cure for HIV, which causes Aids, or acquired immune deficiency syndrome, is still a "long way off".
Professor Roy Chan, who is on the governing council of the International Aids Society and president of Action for Aids, told The Straits Times: "(The virus) infects and multiplies in a variety of organs - these include the brain, lymph nodes, genital tract and gut. These organs are reservoirs of HIV that are not treated and cannot be eliminated by conventional antiretroviral treatment.
"However, researchers have been making major strides in understanding HIV infection and how it causes disease. They are testing out new approaches to overcoming the challenges to effective vaccines... Furthermore new ideas to mitigate the damaging effect of HIV on the body are being studied."
Data from the United States Centres for Disease Control and Prevention shows that the risk of getting HIV varies depending on the type of exposure.
The risk of getting HIV from an infected partner during penile-vaginal intercourse is less than 10 per 10,000 exposures, while the risk from a receptive anal intercourse is 138 per 10,000 exposures.
HIV attacks the immune system and is transmitted mainly through sexual intercourse, although it can spread in other ways, such as by sharing contaminated needles.
Prof Chan noted that an HIV-infected person who is on antiretroviral therapy and has no detectable virus in the blood is also "significantly less infectious to his or her sexual partners". Antiretroviral therapy can reduce the amount of HIV in the blood, enabling the immune system to recover and function almost normally.
"The risk however is not zero. Condoms are advised to prevent other sexually transmitted infections," he added.
According to the World Health Organisation, HIV and Aids remain one of the world's most significant public health challenges.
An estimated 36.9 million people were living with HIV globally as of the end of last year. Health Ministry statistics show that the number of HIV-infected Singapore residents was 6,685 as of the end of last year. Of these 1,737 have died.