When referring to herpes , most people think of a sexually transmitted infection (STI) that causes an outbreak of painful sores on the genitals (sex organs). But, herpes can also affect the anus, leading to anal herpes.
Like genital herpes, anal herpes is caused by the herpes simplex virus (HSV). Anal herpes is usually transmitted by anal sex but, in some cases, can also be transmitted through oral sex.
Studies have shown that most people who get HSV will not develop symptoms (or have only mild symptoms) but can still pass the virus to others without knowing it.
This article looks at the causes and symptoms of anal herpes and describes how this common STI is diagnosed, treated, and prevented.
Herpes simplex virus (HSV) belongs to a family of viruses known as Herpesviridae, which also includes the varicella-zoster virus (VZV) that causes chicken pox and shingles, the Epstein-Barr virus (EBV) that causes mononucleosis and some cancers, and cytomegalovirus (CMV).
Infections with herpes viruses are lifelong. This means that you once you get the virus, it never goes away. Instead, it stays in the body in a latent (dormant) form and can reactivate at any time to cause symptoms.
Several factors differentiate HSV from other types of herpes viruses:
The majority of anal herpes infections are caused by herpes simplex virus type 2 (HSV-2). This is one of two strains of HSV that is transmitted by sexual contact. It accounts for most anal herpes cases worldwide.
The other type that can cause anal herpes is herpes simplex virus type 1 (HSV-1). This is the type that is mainly associated with cold sores but can also be transmitted to the anus via oral sex.
While HSV-2 is the predominant cause of genital herpes, HSV-1 accounts for an increasing number of cases, according to the Centers for Disease Control and Prevention (CDC).
HSV-2 is one of the most common STIs in the world today. According to the CDC, roughly 1 in 8 people in the United States between ages 14 and 49 have acquired HSV-2. With that said, the vast majority are unaware they have the virus because they are either asymptomatic (without symptoms) or subclinical (without readily observable symptoms).
In 2021, an estimated 572,000 people nationwide had newly acquired HSV-2.
The risk of HSV-1 is even greater. The CDC suggests that 3 out of every 5 people in the United States will have HSV-1 by age 50, accounting in part for the rising number of HSV-1-associated anal and genital infections.
Both HSV-1 and HSV-2 are transmitted by contact with someone in whom the virus has reactivated. With reactivation, a phenomenon called viral shedding occurs, in which infectious viral particles are literally shed from the body.
Although the greatest quantity of HSV is shed through open sores, the virus can also be shed through intact skin at the site of the original infection. In fact, most sexual transmissions of HSV-2 occur during periods of asymptomatic shedding.
Anal HSV-2 is primarily transmitted through anal sex. Hand-to-anal transmission is also possible (such as by fingering the anus after touching a sore). It is also possible to auto-inoculate by touching a sore on your own body and then your own anus.
Anal HSV-1 is primarily passed through oral-anal sex (also known as "rimming").
Once you get HSV-1 or HSV-2, you will have it for a lifetime. As such, it is considered a chronic (persistent) infection. This doesn't mean that it will manifest with the same frequency or severity of symptoms in all people—or cause any symptoms at all.
For those who develop symptoms, it is possible to have only one outbreak and never have another. With that said, you are more likely to have repeated episodes, called outbreaks, especially during the first year.
Even so, the frequency and severity of these outbreaks tend to wane over time.
According to a 2018 study in the Journal of Infectious Diseases, up to 25% of people with HSV-2 will experience recurrent outbreaks, averaging around four outbreaks per year.
In the end, there is no way to tell who will develop anal herpes symptoms, how severe symptoms will be, or whether they will have frequent or few outbreaks.
Anal herpes can cause an outbreak of small, watery blisters in and around the anus that eventually erupt into painful open sores. The oozing sores will then quickly crust over and start the process of healing.
During the initial outbreak, the blisters may be preceded by flu-like symptoms, including headache, fever, muscle aches, fatigue, and swollen lymph nodes in the groin. Subsequent outbreaks tend to be far less severe than the first.
As per its name, anal herpes affects the skin and/or mucous membranes around the anus and in the rectum.
Like all herpes viruses, HSV-1 and HSV-2 persist in the body by entering nerve cells near the spinal cord. During the prolonged periods of latency, the virus will lie dormant, largely unseen by the immune system.
If and when the virus reactivates, it will snake its way through a path of nerve cells to the surface of the skin. In the skin, it starts to make and shed copies of itself, whether blisters are formed or not.
Reactivation is isolated to the site of the original infection unless the virus is passed to another part of the body.
An anal herpes blister is typically small, only 1–3 millimeters (less than 1/8 inch) in size, The blisters can sometimes converge into larger blisters and eventually erupt into a reddened, inflamed skin ulcer.
The outbreak of herpes blisters typically occurs in clusters known as crops. The blisters will have a small, fluid-filled head that will pop either spontaneously or when rubbed or scratched.
The resulting skin ulcer has characteristic features, including:
Pain is a common feature of anal herpes. The pain stems from inflammatory damage caused to nerves as the virus reactivates, leading to nerve pain known as hyperalgesia .
The pain from anal herpes can be severe, especially during bowel movements or straining. The abrasion caused by a passing stool or wiping the anus can sometimes cause excruciating pain.
In some cases, the nerve pain will extend beyond the site of the anal sores to one or both sides of the tailbone.
Even so, not all herpes sores are painful. Some people may only experience mild burning or itching. Others may describe pins-and-needles sensations.
There is often no rhyme or reason as to why HSV-2 reactivation occurs or why some people are more prone to reactivations than others. With that said, there are common triggers for herpes reactivation, including illness, stress, and fatigue. Menstruation can also trigger an outbreak.
Roughly 50% of people with recurrent anal herpes will have early warning signs of an outbreak, known as prodromal symptoms . These symptoms may start hours or days before anal blisters appear, often with itching, tingling, or pain in the buttocks, legs, or hips.
People will sometimes mistake prodromal symptoms of anal herpes for sciatica (nerve pain that travels down the legs).
Anal herpes can usually be diagnosed with a physical exam, a review of your medical history, and a swab of the anal sores.
The swab can be used to undergo a nucleic acid amplification test (NAAT), the most sensitive form of testing that identifies HSV based on its genetic material. If this is not available, the swab can also be used to culture (grow) the virus in the lab to make a positive identification.
There are also blood tests that can detect immune proteins, called antibodies, that the immune system produces in response to HSV-1 or HSV-2. While the blood tests may be able to identify which type of HSV you have, they usually cannot tell you when you acquired the virus.
HSV blood testing is only recommended for people with herpes symptoms. The routine screening of HSV for asymptomatic people is not recommended. It has not been shown to change sexual behaviors or slow transmission.
Having herpes does not mean you cannot have sexual relations with someone who does not have herpes. With that said, you need to take precautions and speak honestly with any sexual partner you have.
This may require you to educate your partner about:
If your partner is concerned or you have difficulty communicating with your partner, schedule an appointment with a healthcare provider to sit down and speak with you both.
While safer sex practices are key to prevention, other preventive tools are available. This includes the daily use of antiviral drugs in people with recurrent herpes, which reduces the frequency of outbreaks by 70% to 80% and reduces the risk of transmission to sex partners.
There is no cure for anal herpes. Rather, the infection is treated with antiviral drugs. The three antivirals commonly used to treat anal herpes, which can be taken with or without food, are:
The choice, dose, and duration of treatment can vary based on whether this is your first outbreak or one after the first (called subsequent outbreaks).
Subsequent outbreaks should ideally be treated within 72 hours of the first appearance of blisters. Treatment can even be started before this if you recognize the prodromal signs of an outbreak.
People with frequent outbreaks can ask a healthcare provider about suppressive HSV therapy in which a low-dose antiviral is taken daily to reduce the frequency and severity of herpes outbreaks. This may be a good option for serodiscordant couples, meaning one partner has herpes, but the other doesn't.
The first episode of anal herpes typically occurs two to 12 days (an average of four days) after exposure to the virus. The appearance of blisters and sores can persist for around 10 to 15 days, gradually waning as the viral shedding decreases.
Once the sores are crusted over and no new blisters form, healing usually occurs within two to four weeks. Typically, the sores leave no permanent scars.
Subsequent outbreaks tend to be shorter and less severe. For these outbreaks, viral shedding may only last three days rather than weeks.
The consistent use of condoms is the cornerstone of STI prevention, including anal herpes. However, unlike many other STIs, condoms are less effective in preventing herpes because viral shedding can occur on parts of the body not covered by a condom. This includes the buttocks and groin.
To reduce the risk of transmission, people living with anal herpes need to employ additional prevention strategies, including:
Anal herpes is a sexually transmitted infection (STI) primarily caused by the herpes simplex virus type 2 (HSV-2). Less commonly, anal herpes can be caused by herpes simplex virus type 1 (HSV-1) the type commonly associated with cold sores.
Anal herpes causes the outbreak of tiny blisters around the anus that break open to form painful ulcers. After oozing and crusting, the sores tend to heal within two to four weeks.
Anal herpes can be spread by direct contact with a sore but can also be passed through skin-to-skin contact with someone who has HSV-2 but no symptoms.
While there is no cure for anal herpes, outbreaks can be treated with antiviral drugs. You can also reduce the risk of transmission by using condoms and dental dams, daily antiviral drugs to suppress the virus, avoiding sex during outbreaks, and reducing your number of sex partners.
Because herpes is not life-threatening and tends to become less severe over time, some people don't take it quite as seriously as something like human immunodeficiency virus (HIV). That could be a mistake.
Having anal herpes can increase your risk of getting HIV. On the one hand, the open sores provide HIV easier access into the body. On the other, an acute outbreak draws the very immune cells to the site of infection (called CD4 T-cells) that HIV likes to infect.
If you have HIV, a herpes outbreak can help pass the virus by increasing the rate of HIV shedding. This increases the amount of HIV in semen, vaginal fluids, and anal secretions and, in turn, the risk of transmission.
It is important to remember that safer sex practices, including the consistent use of condoms, afford protection against all STIs, including HIV.
Hemorrhoids (swollen and inflamed veins in the anus and rectum) can cause anal itching and pain similar to anal herpes.
With anal herpes, there will typically be a cluster of red blisters around the anus that will break open to form painful sores. Hemorrhoids will typically cause a more generalized swelling and a pillow-like lump around the anus.
While it can be difficult to tell someone you have herpes, focus on educating your partner about what herpes is, how it is passed, and ways to prevent it. If needed, ask your partner to go with you to a healthcare provider to get the facts.
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