Infectious Disease: Question 7

Worked solution

Part (a): Pathogen and transmission

HIV/AIDS is caused by the human immunodeficiency virus (HIV), a virus. It is present in body fluids of an infected person, particularly blood and semen, and is transmitted when these fluids pass into another person’s body. Common routes include:

• Unprotected sexual contact, where semen or vaginal fluids carrying the virus enter the body of a partner.
• Sharing needles or syringes contaminated with infected blood, for example among people who inject drugs, or through use of unscreened blood in a transfusion.
• Mother-to-child transmission, where the virus passes from an infected mother to her baby during pregnancy, during birth, or through breastfeeding.

Part (b): Measures to reduce transmission

There is no cure for HIV and, because it is a virus, antibiotics have no effect on it, so control instead relies on reducing opportunities for the virus to pass between people:

• Screening donated blood for HIV before it is used for transfusions, so infected blood is not given to another person.
• Promoting condom use during sexual contact, which acts as a barrier and greatly reduces the transfer of body fluids between partners.

Other valid measures include providing clean needles and syringes to reduce needle-sharing, and giving antiretroviral drugs to HIV-positive pregnant women (and to their newborn babies), which lowers the amount of virus in the mother’s blood and substantially reduces the risk of transmission to the child.

Part (c): Social and economic factors making control difficult

Social factor. Stigma: Strong social stigma around HIV discourages many people from coming forward for testing, for fear of how they will be treated by others if their status becomes known. This means a large number of infected people remain undiagnosed. They are unaware of their infection, may continue behaviours that risk transmitting the virus to others, and cannot begin treatment that would both protect their own health and lower the amount of virus in their blood (reducing how infectious they are).

Economic factor, limited budgets: Testing programmes, trained health workers, and antiretroviral drugs all cost money. With limited public health funding, the city cannot test and treat as many people as it needs to, so a larger proportion of the infected population remains undiagnosed or untreated, and the virus continues to be passed on for longer than it would with adequate funding.

Together, stigma and limited resources reinforce each other: even where testing is available, stigma reduces uptake, and even where people are willing to be tested, limited budgets reduce how much testing and treatment can actually be provided, both factors slow down control of the epidemic in this city.

Final answers

• (a) HIV, a virus, transmitted via body fluids (blood, semen) through unprotected sexual contact, sharing contaminated needles, or mother-to-child transmission during pregnancy, birth or breastfeeding.
• (b) Screening donated blood and promoting condom use (also valid: clean needle provision, antiretroviral drugs including for pregnant mothers).
• (c) Stigma leaves many infected people undiagnosed and still able to transmit the virus, while limited budgets restrict how much testing and antiretroviral treatment can be provided, so both factors together slow the control of HIV/AIDS in the city.