Human Immunodeficiency Virus (HIV) is a viral pathogen that attacks the body's immune cells. Table 1 shows information about new diagnoses of HIV in a metropolitan region over several years.
| Year | Number of new HIV cases in adults aged 15–24 | Number of new HIV cases in adults aged 25–44 |
|---|---|---|
| 2014 | 540 | 2450 |
| 2016 | 610 | 2720 |
| 2018 | 580 | 2510 |
| 2020 | 490 | 2150 |
| 2022 | 340 | 1680 |
State one way that HIV can be transmitted from one person to another.
Describe the trends shown in Table 1 for new cases of HIV in both age groups between 2014 and 2022.
Calculate the ratio of new cases of HIV in adults aged 15–24 to those in adults aged 25–44 in 2022. Give your answer to 3 significant figures in the form N:1N : 1N:1.