Diarrhea is not typically listed as a primary symptom for the most commonly recognized sexually transmitted infections (STIs), such as Chlamydia or Gonorrhea. An STI is an infection passed from one person to another through sexual contact, often involving the exchange of bodily fluids or skin-to-skin contact. While many well-known STIs primarily affect the genital tract, throat, or rectum, a direct link between the infection and acute diarrhea is rare. However, the connection between sexual activity and digestive distress exists through specific types of infections and the systemic effects of certain viruses. Diarrhea in a sexually active person can indicate an infection acquired through a sexual route, a systemic reaction to a virus, or a complication of advanced disease.
Gastrointestinal Infections Spread Through Sexual Contact
Some infections that directly target the gastrointestinal (GI) tract and cause diarrhea can be transmitted during sexual activity, particularly through oral-anal contact. These pathogens are considered enteric infections, meaning they primarily infect the intestines, but their transmission route can be sexual. The bacteria Shigella, which causes shigellosis, is a common example, leading to bloody diarrhea, fever, and abdominal cramps.
Protozoan parasites are another group frequently transmitted this way, including Giardia intestinalis and Entamoeba histolytica (which causes amoebiasis). Giardia infection typically results in watery diarrhea, abdominal cramping, and bloating, while Entamoeba histolytica can cause severe diarrhea or dysentery. Viral Hepatitis A, a liver infection, can also be spread sexually through the fecal-oral route and may cause digestive symptoms like nausea and diarrhea. These are distinct from classic STIs because the pathogens enter the body through the mouth and directly infect the digestive system. They cause diarrhea by irritating the intestinal lining or interfering with nutrient absorption.
Systemic STDs and Acute Digestive Distress
Certain viral STDs can cause diarrhea as a side effect of the body’s overall response to the infection, rather than directly infecting the gut. A notable example is the Human Immunodeficiency Virus (HIV), which can present with flu-like symptoms during the acute seroconversion phase, typically two to four weeks after transmission. Diarrhea is a common part of this syndrome, resulting from the massive inflammatory response the body mounts to initial, rapid viral replication.
The virus attacks immune cells, including those in the intestinal lining, triggering a localized inflammatory reaction that results in acute diarrhea. This diarrhea is generally self-limiting, resolving as the acute phase ends. Hepatitis B and C are also sexually transmissible viruses that primarily target the liver. While they do not cause acute diarrhea, severe liver inflammation can indirectly lead to digestive upset and discomfort.
Secondary Diarrhea in Cases of Immunodeficiency
A more serious cause of diarrhea is seen in the later stages of untreated HIV infection, when the virus has severely compromised the immune system, leading to Acquired Immunodeficiency Syndrome (AIDS). This chronic diarrhea is usually not caused by the HIV virus itself, but by opportunistic infections that a weakened immune system cannot fight. Pathogens that are normally harmless can proliferate and cause severe, persistent diarrhea once the CD4+ T-cell count drops significantly.
Examples include the parasites Cryptosporidium and Microsporidium, which cause profuse watery diarrhea. The Cytomegalovirus (CMV) can reactivate and cause colitis, an inflammation of the colon, leading to painful and chronic diarrhea. This type of diarrhea is a complication of advanced immunodeficiency, signaling a failure of the body’s defenses against common environmental microbes.
Testing and When to See a Doctor
Any persistent or severe change in bowel habits, especially diarrhea lasting more than a few days, warrants a medical evaluation. If the diarrhea is accompanied by fever, blood, or mucus in the stool, or symptoms of dehydration, a doctor should be consulted immediately. Patients should be open about their recent sexual history, as this information is necessary for appropriate diagnostic testing.
Diagnostic Procedures
Testing for diarrhea related to sexual contact often begins with a stool sample to check for enteric pathogens like Shigella, Giardia, and Entamoeba histolytica using culture or molecular tests. If an STI is suspected, blood tests screen for systemic viruses like HIV and Hepatitis, or swabs check for common bacterial STIs. Early diagnosis is important because the treatment for a parasite is different from the treatment for a systemic viral infection, and both differ from the management of opportunistic infections in immunodeficiency.