The shape of the lesson
By the end of the lesson, learners can
- HIV, an STI: The lab models a community of 70 people, three of them infected at the start.
- Controlling the spread: Each control measure in the sim breaks one route of transmission.
- STI: an infection transmitted through sexual contact.
- HIV is a virus that causes an STI; infection may lead to AIDS.
- Routes: unprotected sex, shared needles, infected blood, mother to baby.
- Control: condoms, fewer partners, testing and treatment, clean needles, screening blood, education.
One picture every idea returns to
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.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, Stopping an infection that spreads by contact.. Some pathogens are passed from person to person mainly through sexual contact. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 17 min | Teach and check: HIV, an STI | The lab models a community of 70 people, three of them infected at the start. Project tab 7 of the lab (STIs and HIV) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Controlling the spread | Each control measure in the sim breaks one route of transmission. | Cooperative Concept Mapping |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 16 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Controlling the spread, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Cooperative Concept Mapping
Teams receive the key terms on cards and arrange them on a large sheet, drawing and labelling the links. Compare maps between teams before showing the model map.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| 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". |
| Antibiotics do not kill viruses, so they cannot cure HIV. | Treatment with antiviral drugs controls HIV but does not remove it from the body. |
Sexually transmitted infections: worksheet
6 questions, 16 marks. Written in the style of the papers; no past paper question is reproduced.
State what is meant by a sexually transmitted infection and name the virus that causes one.
Describe three ways in which HIV can be transmitted.
Explain the link between HIV and AIDS.
Explain how four different measures can control the spread of STIs such as HIV.
A computer model of 70 people started with 3 infected. After 10 years, 41 were infected with no control measures and 9 were infected when condoms and clean needles were used.
(a) Calculate the percentage of people infected after 10 years in each case. (b) Explain why the control measures had this effect.
A person with an HIV infection is given antibiotics by mistake. Explain why the antibiotics will not cure the infection.
Answer key and marking notes
- An infection that is transmitted through sexual contact.
- HIV (human immunodeficiency virus).
- Unprotected sexual contact with an infected person.
- Sharing needles (e.g. among drug users) or transfusion of infected blood.
- From an infected mother to her baby across the placenta, during birth or in breast milk.
- HIV infects and destroys lymphocytes, so over time the immune system is weakened.
- The person may then develop AIDS and catch other infections that the body cannot fight.
- Using condoms: a barrier that prevents exchange of body fluids during sex.
- Having fewer sexual partners: reduces the number of contacts through which infection can pass.
- Testing and treatment (with contact tracing): infected people know their status, are treated and can protect partners; treatment lowers the virus level.
- Not sharing needles / screening donated blood / education (any one, with explanation).
- (a) No measures: 41 ÷ 70 × 100 = 58.6% (59%). With measures: 9 ÷ 70 × 100 = 12.9% (13%).
- (b) Condoms act as a barrier, so fewer infections pass on through sexual contact.
- Clean needles stop the virus spreading through blood between people who inject drugs.
- HIV is a virus.
- Antibiotics act on bacteria and do not affect viruses (viruses have no cell structures for antibiotics to target).
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which describes a sexually transmitted infection?
- AAn infection that is transmitted through sexual contact
- BAn inherited disease passed from parent to child
- CA disease caused by a lack of a vitamin
- DAn infection spread only by coughing and sneezing
What type of pathogen is HIV?
- Avirus
- Bbacterium
- Cfungus
- Dprotoctist
Which statement about HIV and AIDS is correct?
- AHIV infection may lead to AIDS
- BAIDS is a virus that causes HIV
- CHIV and AIDS are two names for one virus
- DAIDS is passed on but HIV is not
Which way of passing on HIV would screening all donated blood prevent?
- ATransfusion of infected blood
- BUnprotected sexual contact
- CSharing needles between drug users
- DMother to baby in breast milk
Which way of controlling the spread of STIs works by acting as a physical barrier?
- AUsing condoms
- BTesting and treatment
- CHaving fewer sexual partners
- DEducation about STIs
The graph shows a model of HIV infection in a community of 70 people. About how many more people were infected after 10 years with no control measures than with them?
- AAbout 41
- BAbout 49
- CAbout 8
- DAbout 58
In the same model, testing and treatment slows the spread of HIV even though treated people are still infected. Why?
- ATreatment lowers the amount of virus, so it is less likely to be passed on
- BTreatment makes people immune to the virus
- CTreated people can no longer develop AIDS or pass on HIV
- DTesting kills the virus in the people who are tested
Why is HIV not passed on by shaking hands or sharing a cup with an infected person?
- AHIV is passed on in body fluids such as blood and semen, not by touch
- BHIV is killed immediately by contact with skin
- CHIV only infects the reproductive organs
- DCups and hands contain antibiotics
Quiz key
An STI is passed on through sexual contact. Inherited and deficiency diseases are not infections; coughing and sneezing spread airborne diseases such as influenza.
HIV is the human immunodeficiency virus. It is not a bacterium, fungus or protoctist, which is one reason antibiotics cannot cure it.
HIV is the virus; over time infection may lead to AIDS, when the immune system fails. AIDS is not a virus, they are not the same thing, and it is HIV that is transmitted.
Screening removes infected blood before transfusion. It does not affect sexual contact, needle sharing or breast feeding, which need condoms, clean needles or medical advice.
A condom is a barrier that stops body fluids passing between partners. Testing and treatment reduce the amount of pathogen, fewer partners reduces contacts, and education changes behaviour; none is a physical barrier.
At 10 years the red line is at about 49 and the green line at about 8, so the difference is about 41. 49 and 8 are the two single readings, and 58 adds them instead of subtracting.
Antiviral treatment lowers the amount of virus in the blood, greatly reducing the chance of passing it on. It does not give immunity or a cure, it cannot guarantee zero risk, and a test does not kill viruses.
HIV is transmitted in body fluids (blood, semen, vaginal fluid, breast milk), so casual contact does not pass it on. It is not instantly killed by skin, it infects lymphocytes rather than only reproductive organs, and antibiotics do not act on viruses anyway.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.