15.3 Sexually Transmitted Infections

Sexually transmitted infections (STIs) come in bacterial, viral, and parasitic forms, each with unique characteristics and health impacts. These infections spread through sexual contact, affecting millions worldwide and posing significant public health challenges.

Understanding STIs is crucial for prevention and management. From common infections like chlamydia to life-altering viruses like HIV, recognizing symptoms, transmission routes, and treatment options helps individuals protect themselves and others from these widespread health threats.

Bacterial, Viral, and Parasitic STIs

Types of sexually transmitted infections

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• Bacterial STIs attack and multiply in host cells
  • Chlamydia causes urethritis and cervicitis
  • Gonorrhea infects mucous membranes (urethra, cervix)
  • Syphilis progresses through distinct stages affecting multiple organs
• Viral STIs integrate into host DNA, often chronic or recurrent
  • HIV targets immune system leading to AIDS
  • HSV causes recurrent genital herpes outbreaks
  • HPV can lead to genital warts and cervical cancer
  • HBV infects liver cells causing acute or chronic hepatitis
• Parasitic STIs live on or within host, feeding off nutrients
  • Trichomoniasis infects urogenital tract causing inflammation
  • Pubic lice (crabs) infest pubic hair causing intense itching

Characteristics of common STIs

• Chlamydia
  • Transmission through sexual contact with infected mucous membranes
  • Often asymptomatic making detection challenging
  • Abnormal vaginal discharge or urethral discharge in men
  • Burning sensation during urination (dysuria)
  • Complications include PID, epididymitis, and infertility
• Gonorrhea
  • Transmission via sexual contact with infected person
  • Green or yellow purulent discharge from genitals
  • Painful urination (dysuria) and urethral inflammation
  • Complications involve PID, disseminated gonococcal infection, infertility
• Syphilis
  • Transmission through sexual contact and vertical transmission (mother to fetus)
  • Progresses through distinct stages with varying symptoms:
    1. Primary: Painless chancre at infection site
    2. Secondary: Widespread rash, fever, lymphadenopathy
    3. Latent: Asymptomatic period with positive serology
    4. Tertiary: Gummas, cardiovascular and neurological manifestations
  • Complications include neurosyphilis, cardiovascular syphilis, congenital syphilis
• Genital Herpes
  • Transmission via skin-to-skin contact, including during asymptomatic shedding
  • Painful blisters or sores in genital area, recurring outbreaks
  • Flu-like symptoms during initial outbreak (fever, body aches)
  • Complications increase risk of HIV transmission, potential neonatal herpes

HIV and AIDS pathophysiology

• HIV pathophysiology disrupts immune function
  • Retrovirus specifically targets and destroys CD4+ T cells
  • Reverse transcriptase enzyme allows viral RNA to integrate into host DNA
  • Gradual depletion of CD4+ T cells leads to immunodeficiency
• HIV transmission occurs through exchange of bodily fluids
  • Sexual contact with infected person (vaginal, anal, oral)
  • Sharing needles or other drug paraphernalia
  • Mother-to-child transmission during pregnancy, childbirth, or breastfeeding
  • Blood transfusions (now rare in developed countries due to screening)
• HIV infection progresses through distinct stages
  1. Acute HIV infection: Flu-like symptoms, high viral load, rapid CD4+ decline
  2. Chronic HIV infection: Asymptomatic period, gradual CD4+ T cell decline
  3. AIDS: CD4+ count below 200 cells/mm³, opportunistic infections emerge

Prevention and management of STIs

• Prevention strategies reduce transmission risk
  • Safe sex practices include consistent condom use, dental dams
  • Regular STI testing identifies infections early
  • PrEP prevents HIV acquisition in high-risk individuals
  • Vaccinations protect against HPV and Hepatitis B
• Early detection benefits both individuals and public health
  • Reduces transmission risk by identifying asymptomatic carriers
  • Improves treatment outcomes through prompt intervention
  • Prevents complications associated with untreated infections
• Appropriate treatment crucial for individual and community health
  • Proper antibiotic use prevents development of resistant strains
  • Reduces risk of long-term health consequences (infertility, chronic pain)
  • Decreases transmission rates within communities
• Untreated STIs lead to severe long-term health consequences
  • Infertility due to PID or epididymitis
  • Chronic pelvic pain syndrome
  • Increased susceptibility to HIV infection
  • Pregnancy complications (ectopic pregnancy, preterm birth)
  • Certain cancers (cervical, anal, penile) linked to HPV infection