Many people believe that maintaining an exclusive, long-term relationship eliminates the risk of acquiring a sexually transmitted infection (STI). This assumption overlooks the complex biological nature of many STIs. The answer to whether an STI can be contracted while sleeping with the same person is yes, due to biological factors. These factors include the silent nature of some infections, limitations of diagnostic testing, and the periodic re-emergence of dormant infections.
Understanding Latent and Asymptomatic Infections
Many STIs can lie dormant or cause no noticeable symptoms for extended periods, a state known as asymptomatic carriage. This means one partner may have acquired the infection long before the relationship began and carried it unknowingly. The infection is present within the body, but the immune system is containing it or the organism does not produce overt signs.
Bacterial infections, such as Chlamydia and Gonorrhea, are frequently asymptomatic, especially in women, and can remain undetected for weeks or months. Syphilis also has a “latent” stage where all symptoms disappear, but the infection persists and can be transmitted. This silent presence allows the infection to be passed on years later. A positive diagnosis in one partner does not necessarily indicate a recent exposure, but rather the infection finally becoming active enough to cause symptoms or transmit.
The Role of Testing Window Periods
Another factor that can lead to an STI diagnosis within a dedicated couple is the “window period” in diagnostic testing. The window period is the time between infection and when the body produces enough antibodies or viral particles for a test to detect the infection. If a partner gets tested too soon after exposure, the result can be a false negative, meaning they are infected but the test cannot confirm it.
For common infections, this window period varies significantly. Gonorrhea and Chlamydia tests may be accurate within two weeks of exposure, but Syphilis can require up to 90 days for certain antibody tests to become conclusive. If one partner was infected just before or at the beginning of the relationship and tested prematurely, they may have received a clean bill of health while unknowingly carrying the infection. Transmission then occurs later within the relationship, leading to the other partner’s eventual diagnosis.
Reactivation of Dormant Viruses
Certain STIs are caused by viruses that, once acquired, remain in the body for life by integrating into the host’s cells. These viral infections are characterized by periods of latency, where the virus is inactive, followed by periods of reactivation or “flares.” This mechanism is particularly relevant for the Herpes Simplex Virus (HSV) and the Human Papillomavirus (HPV).
The Herpes Simplex Virus retreats into the sensory nerve ganglia near the spinal cord after the initial infection. It remains dormant until a trigger—such as stress, illness, or hormonal changes—causes it to travel back down the nerves to the skin’s surface, resulting in an outbreak of sores. Transmission can occur during these active outbreaks. The virus can also be passed on through “asymptomatic shedding,” where viral particles are released from the skin even when no visible symptoms are present.
Similarly, HPV can remain undetectable for years before it causes symptoms like genital warts or abnormal cell changes. The virus was acquired long ago, but its manifestation or shedding occurs years into the relationship. In these cases, the transmission event is not a recent acquisition from outside the relationship. Instead, it is the passing of a long-dormant virus from one partner to the other during an episodic shedding event.