print small large

This application is a service of the Singapore Government.

Health Sciences Authority

About AIDS and HIV


HIV infection is caused by the Human Immunodeficiency Virus (HIV I & II). The end stage of this disease is called Acquired Immune Deficiency Syndrome (AIDS).

HIV infection is spread mainly through:

  • Sexual contact with an infected person
  • Sharing contaminated needles, such as those used by intravenous drug abusers
  • Transfusion of contaminated blood (rarely)
  • From a HIV-infected mother to her unborn baby

People with AIDS have poorer resistance against infection because their body resistance mechanisms are weakened. Hence, they may develop severe and fatal infections like pneumonia and rare forms of cancer.

Most people who have been infected with HIV do not know that they carry the virus because they may look and feel completely well.

HIV Infection and Blood Donation

During the early stage of infection called the "window period", the virus may not be detected by the best available laboratory tests. However, the blood of infected people can still pass the HIV virus to those who receive it.

This is why people who may be exposed to HIV must not donate blood even if their HIV test is negative.

Who Should Not Donate Blood

People with an increased risk of developing HIV infection must not give blood. They include:

  • People who have had a positive HIV test
  • People with HIV/AIDS
  • People who have had sex with multiple partners
  • People who engage/have engaged in casual sex
  • Men who have/have had sex with other men
  • People who are/were injecting drug users
  • People who have paid for sex
  • Commercial sex workers
  • People with signs and symptoms of AIDS i.e. weight loss, swollen glands in the neck, armpits or groin, persistent diarrhoea or rare cancers
  • Anyone who has had sex with anyone from the above groups

HIV Testing

Do not donate blood if you have engaged in any of the above activities or suspect that you have been otherwise exposed to HIV.

You may wish to undergo HIV testing, which is available at polyclinics and anonymous HIV testing clinics, if you think you may have been exposed to HIV.