Scrollable Chapter Reader
Chapter 24: STIs & HIV/AIDS
Lesson 1 — Understanding STIs
Sexually transmitted infections (STIs) are infections passed from person to person primarily through sexual contact. They are among the most common infectious diseases globally, with teens accounting for nearly half of new U.S. cases.
Bacterial STIsChlamydia, gonorrhea, syphilis — curable with antibiotics if caught early
Viral STIsHIV, herpes, HPV, hepatitis B — no cure, but manageable with treatment
Parasitic STIsPubic lice, trichomoniasis — treatable
AsymptomaticMany STIs have no symptoms — infected people can spread them unknowingly
Testing Matters
Most STIs are asymptomatic. The only way to know your status is to get tested. The CDC recommends annual STI screening for sexually active individuals under 25.
Most STIs are asymptomatic. The only way to know your status is to get tested. The CDC recommends annual STI screening for sexually active individuals under 25.
Quick Check: Why can someone have an STI and not know it?
Lesson 2 — HIV and AIDS
HIV (Human Immunodeficiency Virus) attacks CD4+ T-cells — the commanders of the immune system. Without treatment, HIV progresses to AIDS (Acquired Immunodeficiency Syndrome), when the immune system can no longer fight infections.
Modern HIV Treatment
Antiretroviral therapy (ART) suppresses HIV to undetectable levels. People with undetectable HIV cannot transmit the virus sexually (U=U: Undetectable = Untransmittable). HIV is now a manageable chronic condition, not a death sentence.
Antiretroviral therapy (ART) suppresses HIV to undetectable levels. People with undetectable HIV cannot transmit the virus sexually (U=U: Undetectable = Untransmittable). HIV is now a manageable chronic condition, not a death sentence.
- HIV is transmitted through blood, breast milk, semen, and vaginal fluids
- HIV is NOT spread through casual contact: hugging, sharing food, toilet seats
- PrEP (pre-exposure prophylaxis) is a daily medication that prevents HIV
- Needle exchange programs reduce HIV transmission among drug users
Quick Check: What does U=U mean in the context of HIV treatment?
Lesson 3 — Prevention Strategies
Prevention is the most effective approach to STIs. A combination of behavioral and biomedical strategies provides the strongest protection.
Abstinence100% effective when practiced consistently — the only method that completely eliminates risk
Condoms85–95% effective against STIs when used correctly and consistently
VaccinationHPV and hepatitis B vaccines prevent specific viral STIs
Regular TestingKnowing your status enables timely treatment and prevents unknowing transmission
Quick Check: Name three prevention strategies for STIs and explain how each works.
Lesson 4 — Reducing Stigma & Getting Help
STI stigma prevents people from getting tested, treated, and disclosing their status to partners — making the public health problem worse. Accurate information is the antidote to stigma.
- STIs are medical conditions, not moral judgments — anyone who is sexually active can get one
- Early treatment prevents complications (infertility, cancer, organ damage)
- Partner notification is an ethical responsibility — many health departments offer anonymous notification
- Planned Parenthood and local health clinics offer confidential, low-cost testing
Quick Check: How does stigma make the STI epidemic worse?
Chapter Vocabulary
STISexually Transmitted Infection — an infection passed primarily through sexual contact.
HIVHuman Immunodeficiency Virus — the virus that attacks the immune system and can lead to AIDS.
AIDSAcquired Immunodeficiency Syndrome — the late stage of HIV when the immune system is severely compromised.
Antiretroviral therapyMedication that suppresses HIV to undetectable levels, preventing disease progression and transmission.
ChlamydiaThe most common bacterial STI; often asymptomatic; curable with antibiotics.
HPVHuman Papillomavirus — the most common STI; some strains cause genital warts or cancer; preventable by vaccine.
AbstinenceRefraining from sexual activity; the only 100% effective method to prevent STIs and pregnancy.
PrEPPre-Exposure Prophylaxis — a daily medication that prevents HIV in high-risk individuals.
AsymptomaticHaving an infection without noticeable symptoms.
U=UUndetectable = Untransmittable — a person on effective ART with undetectable HIV cannot sexually transmit the virus.