STD Incubation Periods: When Symptoms Appear and Why Testing Timing Matters

Incubation period = time from exposure to symptom onset. Varies widely by pathogen. Many STDs are asymptomatic; testing windows differ from symptom onset.

Incubation Periods for Common STDs

Infection	Incubation Period	Test Window (NAAT)
Chlamydia	1–3 weeks	1–2 weeks
Gonorrhea	2–7 days	1–2 weeks
Syphilis (primary)	10–90 days (avg 21)	3–6 weeks (serology)
Herpes (HSV-2)	2–12 days	2–12 weeks (serology); PCR if lesion
HIV	2–4 weeks (acute retroviral)	10–33 days (Ag/Ab); 18–45 days (Ab only)
HPV	Weeks to years	Not routinely screened; Pap/HPV test at 21+
Trichomoniasis	5–28 days	1–2 weeks (NAAT)
Mycoplasma genitalium	1–3 weeks	2–3 weeks (NAAT)

Critical Concepts

• Asymptomatic carriage: Chlamydia, gonorrhea, HPV, HIV often have no symptoms.
• Window period: Time after exposure when test is negative despite infection. Test too early → false negative.
• Re-testing: Repeat at window end if initial test negative but exposure high risk.

When to Test

• Symptoms appear → test immediately.
• Known exposure → test at appropriate window (above).
• Routine screening: sexually active <25 annually; new/multiple partners; pregnancy; PrEP users.

Expedited Partner Therapy (EPT)

Available for chlamydia/gonorrhea in many jurisdictions: treat partners without exam.

Early detection prevents complications (PID, infertility, neonatal transmission, systemic spread) and onward transmission.