Like all viruses, HIV cannot grow or reproduce on its own. In order to make new copies of itself it must infect the cells of a living organism
Unlike
most bacteria, HIV particles are much too small to be seen through an
ordinary microscope. However they can be seen clearly with an electron
microscope.
HIV is spread primarily by:
Not using a condom when having sex with a person who has HIV. All unprotected sex with someone who has HIV
contains some risk. However:
Unprotected anal sex is riskier than unprotected vaginal sex.
Among men who have sex with other men, unprotected receptive anal sex is riskier than unprotected insertive anal sex.
Having multiple sex partners or the presence of other sexually transmitted diseases (STDs) can increase the risk
of infection during sex. Unprotected oral sex can also be a risk for HIV transmission, but it is a much lower risk than anal
or vaginal sex.
Sharing needles, syringes, rinse water, or other equipment used to prepare illicit drugs for injection.
Being born to an infected mother-HIV can be passed from mother to child during pregnancy, birth, or breast-feeding.
Less common modes of transmission include:
Being “stuck” with an HIV-contaminated needle or other sharp object. This risk pertains mainly to healthcare workers.
Receiving blood transfusions, blood products, or organ/tissue transplants that are contaminated with HIV.
This risk is extremely remote due to the rigorous testing of the U.S. blood supply and donated organs/tissue.
HIV may also be transmitted through unsafe or unsanitary injections or other medical or dental practices. However, the
risk is also remote with current safety standards in the U.S.
Eating food that has been pre-chewed by an HIV-infected person. The contamination occurs when infected blood from
a caregiver’s mouth mixes with food while chewing. This appears to be a rare occurrence and has only been
documented among infants whose caregiver gave them prechewed food.
Being bitten by a person with HIV. Each of the very small number of cases has included severe trauma with extensive
tissue damage and the presence of blood. There is no risk of transmission if the skin is not broken.
Contact between broken skin, wounds, or mucous membranes and HIV-infected blood or blood-contaminated
body fluids. These reports have also been extremely rare.
There is an extremely remote chance that HIV could be transmitted during “French” or deep, open-mouth kissing
with an HIV-infected person if the HIV-infected person’s mouth or gums are bleeding.
Tattooing or body piercing present a potential risk of HIV transmission, but no cases of HIV transmission from these
activities have been documented. Only sterile equipment should be used for tattooing or body piercing.
There have been a few documented cases in Europe and North Africa where infants have been infected by unsafe
injections and then transmitted HIV to their mothers through breastfeeding. There have been no documented cases of
this mode of transmission in the U.S.
HIV cannot reproduce outside the human body. It is not spread by:
Air or water.
Insects, including mosquitoes. Studies conducted by CDC researchers and others have shown no evidence of HIV
transmission from insects.
Saliva, tears, or sweat. There is no documented case of HIV being transmitted by spitting.
Casual contact like shaking hands or sharing dishes. Closed-mouth or “social” kissing.
