Sexually-transmitted infections

Definition

• infections that are commonly transmitted by sexual activity
  • vaginal sex
  • anal sex
  • oral sex

Epidemiology

• Syphilis in pregnancy > 350,000/year adverse birth outcome
• Cervical cancer due to HPV
• Infertility due to gonorrhea and chlamydia
• HIV, needless to say

• considerations
  • no significant non-human reservoirs
  • role of sexually active groups
  • highlye dependent upon human behavior

[math]\displaystyle{ R_0 = B \times C \times D }[/math]

• [math]\displaystyle{ B }[/math]: transmission coefficient
• [math]\displaystyle{ C }[/math]: mean rate of partner change
• [math]\displaystyle{ D }[/math]: mean duration of infectiousness

• mode of propagation
  • core groups ⇄ bridging population ⇄ general population
  • size of each group differs among different countries

Presentations

genital ulcer

• herpes simplex
• syphilis
• chancroid
• donovanosis
• LGV
• undetermined

urethral discharge

• vaginal discharge
• inguinal swelling
• scrotal swelling
• lower abdominal pain
• neonatal conjunctivitis
• warts/carcinoma
• hepatitis
• fever

Treatment

• WHO has published Tx guidelines for each of STIs
• syndromic management algorithms, e.g. by MSF, are more effective in high STI burden situation without advanced diagnostics
  • disadvantages of over treatment
    • e.g. use penicillin, azithromycin and aciclovir for genital ulcer (against each of syiphilis, chancroid and HSV)
  • disadvantages for women
    • problems with partner notification; stigmatization
    • only symptomatic STIs treated