NB: Unless otherwise indicated,
information in this chapter is summarised from NAM's publication HIV transmission & testing.
What scientists understand
about HIV exposure or transmission is based on a combination of studying both
the theoretical (what is biologically
plausible) and the epidemiological
(what has actually been seen in the real world). Assessing levels of HIV
exposure or transmission risk requires using a commonsense perspective to
balance these different types of evidence. For example, although it is known
that saliva contains tiny amounts of HIV, and therefore transmission by this
route is biologically plausible, there has never been a documented case of HIV
infection resulting from kissing or spitting. Therefore, experts unanimously
and emphatically agree that neither act imposes any risk of HIV transmission.
HIV is not present in:
HIV is sometimes present in negligible quantities in:
HIV is often
– but not always
– present in large enough quantities to infect in:
conditions need to be met for transmission to occur: HIV
(as a whole virus or as a provirus –
i.e., within cells that contain its genetic material) must be present in an infectious body fluid from the HIV-positive person;
it must be present at sufficient levels to cause infection; there must be an effective
route of transmission; and virus carried to another person via this route must
reach susceptible cells in the other person.
HIV is transmitted
in four main ways:
Via sex. Alleged sexual exposure or transmission are the focus of most HIV-related
Via the use of non-sterile injecting
equipment. The consensual
use of non-sterile injecting equipment without disclosure of HIV-positive
status is against the law in certain jurisdictions,i although few
prosecutions have ever taken place. In very rare cases, individuals wielding
needles/syringes that they claim contain HIV-infected blood have been arrested
There have also been a very small number of cases in which people have
intentionally injected others with HIV.ii Additionally,
medical workers, often working under poor infection-control conditions due to
lack of resources, have sometimes been prosecuted for allegedly infecting
others through the use of non-sterile injecting equipment.iii
From a mother to her infant. Prosecutions for this type of
transmission, which can occur before or during birth, as well as during
breastfeeding, have been extremely rare.3
Via medical use of blood products. HIV can be acquired via blood transfusion
or the use of blood products if the blood has not been screened for HIV.
Screening has taken place in wealthy countries since the mid-1980s, but 41 low-
and middle-income countries are still not able to screen all blood donations.4 Some
jurisdictions have laws against donating HIV-infected blood, but prosecutions are
The likelihood of HIV transmission occurring during sexual intercourse
varies greatly from one situation to another. Factors that may increase or
decrease the level of risk include:
the type of
sexual activity, including whether or not intercourse is forced.
the roles during
penetrative sex, in terms of who is the insertive partner and who is the
the amount of HIV in the bodily fluid to which the at-risk
person is exposed.
the presence or
absence of other sexually transmitted infections (STIs) in both partners.
whether or not the penis has been circumcised.
protective factors in the potentially
exposed partner, for example, the antiviral properties of saliva, and/or
specific or non-specific immune defence mechanisms in genital secretions.
Importantly, most experts agree that the correct use
of a male or female condom, regardless of other factors, subsantially reduces
the risk of HIV transmission.5,6
i. For example, while Canada
allows for prosecutions for HIV exposure via both the consensual use of
non-sterile injecting equipment and consensual sex, but has only
only criminalises transmission via the consensual use of non-sterile
equipment: there are no laws against sexual transmission.
See: No laws on HIV. Fiji Times, 21 April 2008.
ii. See, for example: ‘Father
is guilty in HIV case’. New York
Times 6 December 1998; Bernard EJ ‘Four
Dutch men accused of “premeditated” criminal HIV transmission via rape and
injection’. www.aidsmap.com, 1 June 2007; Eight
years' prison for HIV infection. Sunday
Star Times, 7 Feb 2010.
iii. For example, in 1999, six healthcare workers (five Bulgarian
and one Palestinian doctor) were accused of deliberately infecting
with HIV while working at a hospital in Benghazi,
Libya, and received life
sentences from a Libyan court; they were pardoned by the Bulgarian
upon their negotiated transfer to Bulgaria in 2007. Also in 2007, 21
Kazakh medical workers were found guilty of intentionally infecting
with HIV and were sentenced to up to five years in prison. See: BBC Online. ‘HIV medics released to
Bulgaria’ http://news.bbc.co.uk, 24 July 2007; Kaiser Network ‘Doctors in Kazakhstan on
trial for medical malpractice following HIV outbreak among children who received
blood transfusions’. www.kaiserhealthnews.org, 20 March
2007; and Associated Press ‘21
convicted in Kazakh AIDS case’. www.ap.org, June 27,
iv. In 2005, Singapore
successfully prosecuted five blood donors whose blood tested
who were unaware they were living with HIV.7 The men had failed to
full sexual history. Prison sentences ranged between eight and ten
similar case – with a prison sentence of 33 months suspended for three
for a man unaware of his infection who failed to report a previous risk
whilst donating blood – occurred in Thessaloniki,
Greece in March