STD Incubation Period. The incubation period for the various STIs (Sexually Transmitted Infections) is a common question asked by patients in our clinics. It refers to the time between acquiring the infection and the presentation of symptoms. This is different from the window period, which refers to the period after infection in which no current available tests are sensitive enough to detect the infection. The window period for the various STIs depends on which tests are used.
As different STIs have different incubation periods, it is not easy to answer the question when symptoms will appear after a particular risky exposure. I will list below the common STIs tested for, their incubation and window period as well as possible initial presentation.
The following are the Common STDs and their incubating periods:
#1 STD Incubation Period – Human Immunodeficiency Virus (HIV)
Early HIV infection refers to approximately 6 months after initial acquisition. It is estimated that 10 to 60 percent of all early HIV infections are asymptomatic, or without any symptoms. For early symptomatic HIV infection, the usual incubation period is around 2 to 4 weeks, although incubation periods as long as 10 months have been observed.
Acute symptomatic HIV infection present with a collection of signs and symptoms known as Acute Retroviral Syndrome (ARS). The most common findings for ARS are fever, sore throat, rash, swollen lymph nodes, body aches and pains. However, all these symptoms are not specific to acute HIV infection, hence please do not panic if you observe these symptoms after a risky encounter. See your doctor for further advice and testing
The Window period for HIV testing depends on the test that is conducted. The initially 10 days after exposure is known as the eclipse period, for which there are no tests that can pick up any infection. The earliest tests that can be done with conclusive results are the HIV ProViral DNA test or the HIV RNA PCR test, which can pick up possible acute infections 10 days after exposure.
4th Generation HIV tests will be conclusive around 28 days after exposure, while 3rd Generation HIV tests will be conclusive around 90 days after exposure.
#2 STD Incubation Period – Syphilis
Approximately 50% of patients diagnosed with syphilis do not have any symptoms. This is because syphilis has 3 stages of infection: Primary, Secondary and Tertiary Syphilis and Primary and Secondary syphilis might have symptoms that are so mild that they are ignored by the patient.
Primary syphilis presents with a painless ulcer on the genitalia, known as a chancre. The incubation period for a chancre appears to range from 3 to 90 days, with an average of around 21 days. The chancre will heal within 3 to 6 weeks even without treatment. Within weeks to a few months after the chancre appears, around 25 percent of untreated individuals will develop Secondary Syphilis.
Secondary Syphilis can present with a widespread rash, ulcers, patchy hair loss, swollen lymph nodes, weight loss and fatigue. The infection subsequently goes into a latent phase lasting for years for which there are no signs or symptoms. This is the reason why the majority of syphilis picked up on routine screening are asymptomatic.
Neurosyphilis occurs when the infection reaches the central nervous system i.e. the brain or spinal cord. Neurosyphilis can occur at any stage of infection, but tends to occur in tertiary syphilis. Therefore, neurosyphilis can occur within a few months, but could also develop after 10 to 30 years, of a syphilis infection.
The window period for syphilis testing depends on the stage of syphilis infection. The blood tests (FTA-ABS and TPPA) will be positive around 1 to 2 weeks after chancre formation.
#3 STD Incubation Period – Hepatitis B and C
The majority of hepatitis B and C infection are asymptomatic. It has been estimated that around 30 percent of acute hepatitis B infection and less than 25 percent of acute hepatitis C infection are symptomatic. Symptoms of acute infection tend to be very mild and may include the following: Fever, Fatigue, Nausea/vomiting, Dark Urine, Pale stools and abdominal pain.
The incubation for acute hepatitis B infection is estimated to be around 1 month to 4 month, while the incubation period for acute hepatitis C infection is estimated to be from 2 weeks to 3 months.
The window period for both hepatitis B and C testing for antibodies is on the average about a month. It will be much shorter if alternate tests such as the Hepatitis C RNA PCR test for Hepatitis B Viral Load are used instead.
#4 STD Incubation Period – Genital Herpes
Genital herpes is caused by both Herpes Simplex Virus 1 or 2 (HSV1/2). Genital herpes infections often do not have symptoms or mild symptoms that go unrecognized. It is estimated that one third of patients with new infections do not have symptoms. The initial presentation of symptoms range from severe with painful genitalia ulcers, painful urination, painful lymph node swellings and fever. However, patients also can have mild or no symptoms as well. The initial presentation does not depends on the type of virus (HSV1 vs HSV2)
The incubation period for genital herpes is around 4 days, with a range from 2 days to 12 days.
For asymptomatic infections, HSV 1/2 Antibodies will start appearing in the serum starting from 3 weeks and majority of patients would have antibodies by 16 weeks. The window period for testing for asymptomatic patients is hence from 3 weeks to 16 weeks. For patients with symptoms of the painful genital ulcers, the test of choice is Nucleic Acid Amplification Testing (NAAT) for which a swab of the ulcer is taken and tested for HSV DNA. There is no window period for NAAT.
Rapid Herpes Testing with Next Day Results is available in all DTAP Clinic in Singapore.
#5 STD Incubation Period – Gonorrhea
Gonorrhea causes different symptoms for men and women. For women, the cervix is the most common site of infection and the common symptoms are vaginal itch and discharge. Some women also have heavier periods or bleeding in-between periods. If the infection has ascended beyond the cervix into the uterus, this is a potentially more dangerous condition known as Pelvic Inflammatory Disease (PID) for which abdomen pain and fever are common symptoms. Up to 70 percent of patients with cervical gonorrhea infection are asymptomatic.
For men, urethritis is the most common presentation of gonorrhea infections. It is characterised by purulent urethral discharge and painful urination. In contrast to infections in women, the majority of infections in men are symptomatic.
- Oral Gonorrhea / Throat Gonorrhea – What do you need to know
- What is Antibiotic Resistant Gonorrhea or Super Gonorrhea?
In women, the incubation period for genital infection is around 10 days. In men, the incubation period for symptomatic infected men is around 2 to 5 days, with 90 percent of these individuals with symptoms of urethritis by 2 weeks.
The accepted standard for testing for gonorrhea infection is NAAT, a urine sample for men and a cervical swab for women. As NAAT is able to detect low numbers of organisms with good accuracy, there is no window period for NAAT testing.
#6 STD Incubation Period – Chlamydia
Chlamydia causes similar symptoms as gonorrhea in both men and women. In women, the cervix is also the most common site of infection with a proportion of patients having a urethra infection as well. However the majority of infected women, around 85 percent of patients are asymptomatic with neither signs or symptoms.
Symptoms of chlamydia infection are similar to gonorrhea in men as well, with a clear to mucoid penile discharge and painful urination. The proportion of asymptomatic infection varies as well in men, ranging from 40 to 96 percent with no symptoms.
The incubation period for symptomatic infection ranges from 5 to 14 days after exposure for both men and women.
The gold testing for testing for chlamydia infection is NAAT as well. There is no window period for NAAT testing.
|Asymptomatic/Mild Infections (%)
|10 to 60
|2 to 4 weeks
|Proviral DNA : 10 days
RNA PCR : 12 days
4th Generation Ag/Ab :28 days
3rd Generation Ag : 90 days
|3 to 90 days
Average 21 days
|FTA-ABS : 1 to 2 weeks after chancre
|1 month to 4 month
|HbsAg : 1 month
|2 weeks to 3 month
|Anti-HCV Ab : 1 month
|2 to 12 days
Average 4 days
|HSV 1/2 IgG : 3 to 16 weeks
HSV DNA PCR : No window period
Men: Majority Symptomatic
Men: 2 to 5 days
|Gonorrhea DNA PCR: No window period
|5 to 14 days
|Chlamydia DNA PCR: No window period
If you like to speak to our doctors on your STD concern, please visit any of our clinics in Singapore & Malaysia.