Can You Get an STI If Both Partners Have No STIs?

Finding out you have a sexually transmitted infection (STI) while in a committed relationship can come as a shock. If neither you nor your partner has been with anyone else, a positive result may immediately raise questions about infidelity. However, a positive STI test doesn't necessarily mean someone has cheated. Below, we explain how STIs can go undetected, what a positive test can tell you, and what steps you can take next.

Why a positive STI result does not always mean cheating

Receiving a positive STI test result in a monogamous relationship can lead to concerns about infidelity. However, a positive result alone does not indicate that either partner has been unfaithful.

Many STIs cause no noticeable symptoms and may have been contracted before the relationship began. Infections such as HPV can remain unnoticed for years. Certain infections can also spread through contact that doesn't involve penetrative sex. For example, oral herpes (HSV-1) can spread through skin-to-skin contact or saliva, including sharing e.g. a fork/spoon or straw.

Sources:

• WHO, 2025

• Cleveland Clinic, 2024

A positive STI result is therefore not proof of infidelity. Understanding how and when an infection may have been acquired can help avoid incorrect assumptions.

How long can an STI stay dormant without symptoms?

How long an STI can remain unnoticed varies depending on the infection. While some cause symptoms within days or weeks, others may go undetected for months or years, or never cause noticeable symptoms at all. Testing is therefore the most reliable way to identify an infection, even when no symptoms are present (NHS, 2024).

It's also helpful to understand the difference between an infection being dormant and asymptomatic. A dormant virus, such as herpes, can remain dormant in nerve cells for long periods before certain factors trigger its reactivation, potentially causing new outbreaks. An asymptomatic infection is present without causing noticeable symptoms, but it may still be active and transmissible.

Sources:

• MedlinePlus, 2024
• Kenyon et al., 2023

STIs that can show no symptoms for long periods

Several common STIs can remain unnoticed for extended periods, as they may cause few or no symptoms:

• Herpes (HSV): Symptoms usually appear within days of infection but may not develop until months or even years later. The virus remains in the body for life.

• Human papillomavirus (HPV): Often causes no symptoms and can remain unnoticed for years. Certain types may eventually cause genital warts or abnormal cell changes that can sometimes turn into cancer.

• Chlamydia: Most people experience no symptoms. When symptoms occur, they can develop between one week and several months after infection.

• Gonorrhoea: Symptoms typically appear within two weeks, although they can take months to develop. Some people have no noticeable symptoms.

• HIV: During an acute HIV infection, flu-like symptoms may appear two to four weeks after infection. In case of a chronic infection, there may be no noticeable symptoms. Without treatment, this stage can last 10–15 years.

Sources:

• NHS, 2023

• NHS, 2026

• NHS, 2024

• NHS, 2024

• HIV.gov, 2026

Can you get an STI without cheating?

Yes, you can get an STI without cheating. There are several possible explanations for a positive test result in a monogamous relationship:

• Infection before the relationship: An STI may have been contracted from a previous partner and gone unnoticed, especially if neither partner was tested at the start of the relationship.

• Inaccurate or incomplete test results: A false negative can occur if testing is done too soon after exposure or if the test does not cover the infection or affected body area. False positives are also possible and may require confirmation.

• Transmission without penetrative sex: Certain STIs, such as herpes, can spread through skin-to-skin contact or saliva, for example through sharing items (e.g. straw, fork/spoon) that come into contact with the mouth.

A healthcare professional can help identify possible explanations based on your medical history and previous test results.

Sources:

• Mayo Clinic, 2024
• Cleveland Clinic, 2024
• Cleveland Clinic, 2023

What are the risks of leaving an STI undiagnosed?

In the short term, STIs can cause symptoms such as genital sores, itching, unusual discharge, bleeding, painful urination or discomfort during sex. Some infections may also cause general symptoms, including fever, fatigue or skin rashes. However, symptoms can also be mild or absent altogether.

Untreated STIs can lead to serious health complications, including:

• Organ and nerve damage

• Infertility in men and women

• Pelvic inflammatory disease (PID)

• Ectopic pregnancy

• Chronic pelvic or testicular pain

• Progression of HIV to AIDS

• Transmission to sexual partners or unborn babies

Early detection is important, as most STIs can be successfully treated.

Source: Cleveland Clinic, 2023

What should you do if you suspect an STI in your relationship?

If you or your partner receives a positive STI result, try to focus on understanding the situation and protecting your health rather than immediately assigning blame.

Here are four practical steps:

1. Get tested together. Both partners should consider appropriate STI testing, even if one has no symptoms. Depending on the infection, repeat or confirmatory testing may be needed.

2. Talk openly and calmly. Share your concerns, previous testing history and possible exposures without assuming that someone has been unfaithful.

3. Avoid unprotected sex for now. Use protection or avoid sexual contact until you've received medical advice about the results, any necessary treatment and when it's safe to resume sex.

4. Speak to a healthcare professional. A doctor or sexual health specialist can explain the findings, discuss possible infection timelines and recommend treatment or further testing.

Source: Cleveland Clinic, 2023

How can you test for an STI discreetly and reliably?

Getting tested doesn't always mean visiting a sexual health clinic. Depending on the infection, STI tests may use a urine sample, a swab, or a blood sample.

For people who prefer privacy, Homed-IQ offers convenient at-home STI testing kits, ranging from the Basic-4 STI Test to more comprehensive testing options. You can collect your sample at home using the instructions provided and send it to the laboratory for analysis. Homed-IQ works with ISO 15189-accredited laboratories, and your results are delivered through a secure online account.

At-home testing can make it easier for both partners to take the next step without an uncomfortable clinic visit. However, not every kit checks for every STI, so it's important to choose the right test and follow up with a healthcare professional if you receive a positive result or have symptoms.

Frequently asked questions

Can you get an STI if neither partner has cheated? Yes, an infection acquired before the relationship may remain undetected and be discovered later (NHS, 2024).

Can an STI show up years after infection? Yes STIs can cause noticeable symptoms years after the original infection (NHS, 2024).

Which STIs are most likely to stay hidden? For example herpes, HPV, HIV, chlamydia and gonorrhoea can all be present without obvious symptoms.

Sources:

• NHS, 2023

• NHS, 2026

• NHS, 2024

• NHS, 2024

• HIV.gov, 2026

Does a positive STI result always mean someone has been unfaithful? No, a positive result does not necessarily prove infidelity.

How can I find out if I had an STI before my current relationship? Previous test results may provide some insight. A healthcare professional can help assess your testing history.

What should we do if one partner tests positive? Discuss the result openly, arrange appropriate testing or treatment, and seek professional medical guidance.