Some pathogens are passed from person to person mainly through sexual contact. HIV is one of them, and without treatment it can slowly destroy the immune system. Knowing exactly how it is transmitted is what makes it possible to control.
A sexually transmitted infection (STI) is an infection that is transmitted through sexual contact. The human immunodeficiency virus (HIV) is a pathogen that causes an STI, and HIV infection may lead to AIDS. HIV is passed on in body fluids: by unprotected sexual contact, sharing needles, infected blood and from mother to baby. The spread of STIs is controlled by using condoms, limiting sexual partners, testing and treatment, and education.
The lab models a community of 70 people, three of them infected at the start. Run it with no control measures and watch the infected count and the years. Then switch on condoms, clean needles, testing and treatment, or fewer partners, and press Restart to compare.
HIV is the virus; AIDS is the condition that may develop later when the immune system fails. Write "HIV infection may lead to AIDS", not "HIV is AIDS".
Four quick checks. Each correct answer earns XP and records this skill on your profile.
In the STI sim, what do the purple rings show?
In the sim, what colour shows that an infected person has developed AIDS?
Which control measure in the sim specifically reduces spread between people who inject drugs?
How does testing and treatment slow the spread in the sim?
Each control measure in the sim breaks one route of transmission. Explaining a measure means saying which route it blocks.
| Control measure | How it reduces spread |
|---|---|
| Using condoms | a barrier that stops body fluids passing between partners during sexual contact |
| Fewer sexual partners | fewer contacts, so fewer chances to pass the infection on |
| Testing and treatment | infected people find out and can be treated; for HIV, treatment lowers the amount of virus in the blood, so it is much less likely to be passed on; partners can be traced and tested |
| Clean needles, not sharing | stops spread through blood |
| Screening donated blood | infected blood is not used for transfusions |
| Treatment in pregnancy; bottle feeding where advised | reduces transmission from mother to baby |
| Education | people know how STIs are spread and how to protect themselves |
Antibiotics do not kill viruses, so they cannot cure HIV. Treatment with antiviral drugs controls HIV but does not remove it from the body.
Unlocks once the four checks above are done. Worth more XP, written to IGCSE Paper 2 and Paper 4 standard.
Which describes a sexually transmitted infection?
Which statement about HIV is correct?
Which is a method of transmission of HIV?
Why does using a condom reduce the spread of STIs?
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