Reproduction: Question 10
Syllabus 16.6
A health clinic identifies three different routes by which HIV can be transmitted between people: through unprotected sexual contact, through contact with infected blood (for example, by sharing unsterilised needles), and from an infected mother to her child (for example, during pregnancy, birth or breastfeeding).
(a) For each of these three transmission routes, state one method that can be used to reduce the risk of transmission by that route. [3]
(b) Suggest why testing donated blood for HIV, before it is used in blood transfusions, is an important part of controlling the spread of HIV within a population. [2]
(c) State one reason why HIV can continue to spread within a population even in places where screening and treatment programmes are available. [1]
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Worked solution
Part (a): Reducing transmission by each route
HIV is transmitted through the transfer of specific body fluids (blood, semen, vaginal fluids, or breast milk), so control measures target each route separately:
- Unprotected sexual contact: using a barrier method of contraception, such as a condom, prevents these body fluids being exchanged during sex.
- Infected blood: always using new, sterile needles and never sharing needles between people prevents infected blood being injected directly into another person’s bloodstream (screening blood used in medical procedures is another valid control here).
- Mother-to-child: receiving appropriate medical care and monitoring during pregnancy and birth, and avoiding breastfeeding where safe alternative feeding methods are available, both reduce the chance of the virus passing from mother to child.
Part (b): Why blood donation screening matters
A person infected with HIV can carry and transmit the virus for a long time before any symptoms appear, so a donor who feels completely healthy could still be infected. If infected blood were used in a transfusion without being detected, HIV would pass directly and efficiently into the recipient’s bloodstream in large quantities. Testing every blood donation before it is used allows infected blood to be identified and discarded, preventing this route of transmission and protecting transfusion recipients who have no way of knowing the infection status of donated blood themselves.
Part (c): Why HIV can still spread despite screening and treatment
Even where screening and treatment programmes exist, HIV can continue to spread for reasons connected to how consistently and widely these programmes are actually used. For example, not everyone has access to, or can afford, regular screening and treatment; some infected people are unaware of their status and continue behaviours that risk transmitting the virus; social stigma around HIV can discourage people from being tested or seeking treatment; and prevention methods such as condoms are not always used consistently by everyone, even where they are available.
Final answers
- (a) Sexual contact – barrier contraception (condoms). Infected blood – sterile, non-shared needles. Mother-to-child – medical care during pregnancy/birth and avoiding breastfeeding where safe alternatives exist.
- (b) Donors can be infected without showing symptoms, so testing prevents infected blood from being transfused into another person.
- (c) One valid reason, e.g. unequal access to screening/treatment, undiagnosed infections, stigma, or inconsistent use of prevention methods.