Acquired immune deficiency syndrome (AIDS), a disease caused by the HIV virus, has resulted in millions of deaths worldwide since it was first identified in 1981.

Explain why viral infections, such as AIDS, are generally more difficult to treat than bacterial infections.

viruses mutate quickly so adapt to drugs/evade immune system response / OWTTE;

bacteria are more complex and thus can be targeted in more ways / viruses lack sub-units/functions targeted by antibacterials / OWTTE;

different types of bacteria employ similar metabolic processes and thus can be targeted by common antibacterials / each kind of virus usually requires special drugs/approaches / OWTTE;

bacteria can be killed by interfering with cell wall production without attacking host cell / difficult to attack the virus without attacking host cell;

Candidates tended to write a lot in this answer – and it was not very well structured. They needed to keep the focus of their answer on the differences between viral and bacterial infections. It may be that the examiners’ intention to help the candidates by setting the question in context turned out to be more of a hindrance. Candidates spent far too long discussing the specifics of HIV rather than answering the question required.