Holiday romances are part of travel, and so, sometimes, are the infections that come with them. Sexually transmitted infections are far more common than HIV, and most are easy to treat once found. The tricky part is that many cause no symptoms at all, and the ones that do can look like other things.
This guide explains what to watch for after a fling, when each infection can be tested for, and how to get checked on Koh Samui or once you are home.
Key points
- Many STIs, especially chlamydia and gonorrhoea, often cause no symptoms.
- Testing too soon can miss an infection. Most tests are accurate from about 2 weeks.
- Throat and rectal infections are common and need specific tests.
- If the fling was within the last 72 hours, ask about HIV PEP as well.
The common culprits
Chlamydia
The most common bacterial STI. Often silent, especially in women. When symptoms appear, they include burning when peeing, unusual discharge, or pain in the lower abdomen or testicles. Easily treated with antibiotics.
Gonorrhoea
Similar symptoms to chlamydia, often appearing within a week or two: discharge, pain when peeing, and sometimes a sore throat or rectal discomfort. Antibiotic resistance is a growing concern, so proper testing and treatment matter.
Syphilis
Starts with a painless sore at the site of contact, which is easy to miss and heals on its own. Weeks later, a rash may appear, often on the palms or soles. Untreated, it can cause serious problems, but it is easily treated early.
Herpes
Painful blisters or sores around the genitals or mouth. Many people carry herpes without ever having symptoms. There is no cure, but treatment controls outbreaks well.
Hepatitis B and C
Often silent for a long time. Hepatitis B is preventable with vaccination. Both are found with blood tests.
HIV
Early HIV can cause flu-like symptoms 2 to 4 weeks after infection, but many people notice nothing. See our guide to when to test for HIV.
When each test becomes reliable
| Infection | Test type | Reliable from about |
|---|---|---|
| Chlamydia | Urine or swab | 2 weeks |
| Gonorrhoea | Urine or swab | 2 weeks |
| Syphilis | Blood | 3 to 6 weeks, recheck at 12 weeks |
| Hepatitis B | Blood | 3 to 6 weeks, up to 12 weeks |
| Hepatitis C | Blood | 8 to 12 weeks |
| HIV | Blood | 6 weeks for most, 3 months final |
If you have symptoms, do not wait for these dates. See a doctor straight away, as symptoms can be tested and treated on the day.
Got symptoms?Burning, discharge, sores or a rash after a new partner are worth checking now. Walk in any time.
Why no symptoms does not mean no infection
A large share of chlamydia and gonorrhoea infections cause no symptoms, especially in the throat and rectum. You can feel completely well and still pass an infection on, or develop complications later. That is why routine testing after a new partner makes sense, even if everything seems fine.
Throat and rectal infections
Standard urine tests only check the genitals. If you had oral or anal sex, ask about throat and rectal swabs or a broader PCR panel. These sites are where infections most often go unnoticed.
Testing on Koh Samui
You can walk in for STI testing at any hour. Our STI packages start at 2,500 baht for HIV, syphilis, hepatitis B and C and a urine test, with options adding gonorrhoea and chlamydia or a 15-pathogen PCR panel. The doctor will help you choose based on your symptoms and the type of contact.
If you are leaving the island soon, you can test here first and repeat any tests at home once enough time has passed.
If a test is positive
Most bacterial STIs are cured with a short course of antibiotics. The doctor will explain your result, the treatment, how long to avoid sex, and whether a retest is needed. It is also important that recent partners are tested and treated, but how you tell them is up to you.
Lowering the risk next time
- Condoms protect well against most STIs, including oral sex with condoms or dams.
- Hepatitis B vaccination is safe, effective and worth getting if you are not protected.
- If you are on PrEP, STI tests every 3 months are part of the routine.
- If you have had a new partner, test even when you feel fine.
Want a full check before you fly home?Choose a package or let the doctor suggest the right tests. First name only.
Frequently asked questions
How soon after sex can I get symptoms?
Gonorrhoea can cause symptoms within days. Chlamydia may take one to three weeks, if it causes any. Syphilis sores usually appear around three weeks after contact.
Can I get tested the day after?
You can, but most tests will not be accurate yet. If the fling was in the last 72 hours, the more urgent question is whether you need HIV PEP.
Do I need to tell my partner?
It is strongly recommended, so they can be treated too. The doctor can advise on how to have that conversation.
Can I catch an STI from oral sex?
Yes. Gonorrhoea, chlamydia, syphilis and herpes can all be passed on through oral sex, which is why throat swabs can be useful.