Question 1
Paper 2Medium16 marksA group of 100 people with HIV was followed from the time their infection was confirmed. Researchers recorded the mean count of a particular type of lymphocyte and the percentage of participants who had at least one opportunistic infection.
| Years after HIV infection was confirmed | Mean lymphocyte count (cells per μL) | Participants with at least one opportunistic infection (%) |
|---|---|---|
| 0 | 900 | 2 |
| 3 | 690 | 6 |
| 6 | 420 | 24 |
| 9 | 180 | 50 |
(a)[3]
Calculate the percentage decrease in mean lymphocyte count between year 0 and year 9.
(b)[4]
Describe the changes in both measurements between year 0 and year 9, using the data.
(c)[2]
Identify the type of lymphocyte infected by HIV and state what HIV does to these cells.
(d)[3]
Explain how the decline in these lymphocytes can lead to AIDS.
(e)[4]
Explain two mechanisms by which HIV can be transmitted in body fluids: one involving blood and one during sexual intercourse.