Sexually transmitted infections

Read up on chlamydia, gonorrhoea, syphilis, herpes, different types of hepatitis and HPV. We explain how they're transmitted, diagnosed and treated. At the bottom of the page, you'll find information about bacterial vaginosis, urinary tract infections and yeast infections; infections that aren't classified as sexually transmitted infections (STIs) but can be good to know about.


Easily transmitted through different types of sex
Condom and lube gives good protection in anal and vaginal intercourse
Often asymptomatic
Testing and treatment are free
Tested with a swab of the genitalia, anus or throat, depending on what kind of sex you’ve had
Treated with antibiotics

Chlamydia is the most common STI in Sweden. It can be hard to detect since it’s often asymptomatic. Half of those infected get no symptoms. About 35 000 people test positive for chlamydia every year (2019).

Chlamydia is transmitted through mucous membranes and the contact between bodily fluids and mucous membranes. It’s most easily transmitted through vaginal and anal intercourse. The best way to reduce the risk of transmission is to use a condom in anal and vaginal intercourse, or to have sex other than intercourse. Chlamydia is easily transmitted. It can affect your genitals, throat and eyes.

Chlamydia is often asymptomatic. If you do get symptoms they vary depending on what part of your body is affected. In the genital area, chlamydia can cause discharge and/or a stinging sensation when you urinate. You may also experience discharge from the anus if that’s where you got infected. Chlamydia in the throat has the same symptoms as strep throat. It’s difficult to transmit a chlamydia infection of the throat, and it often heals on its own.

To avoid that chlamydia is transmitted to the throat you can use condoms in oral sex with a penis. The risk of transmitting chlamydia in oral sex with a vagina or anus is small, even without protection.

There’s a small risk that chlamydia can be transmitted through sex using the hands or by transferring sex toys between different people’s genitals and anuses. You can reduce the risk by avoiding transferring bodily fluids between people for example by washing your hands and changing the condom on sex toys.


Chlamydia is a local infection that can affect different parts of the body. Therefore, you need to get tested in the bodypart where you might have been exposed; the genitals, throat and/or anus. A urine sample is taken to test for chlamydia in the genitals, and, for people with a vagina, this is usually combined with a swab of the inside of the vagina. Swabs are also used in the throat and the anus, and it only takes a couple of seconds. Since chlamydia often is asymptomatic and easily contracted, it’s important to get tested regularly if you sometimes change sex partners.

There are at home tests you can use for chlamydia in the genitals. They can be ordered through the internet or bought at a pharmacy. It’s important to follow the instructions. People with a penis will send a urine sample. People with a vagina will send a urine sample and do a swab of the vagina. The tests are sent to a laboratory for analysis. If you test positive, you need to seek care for treatment. It’s important to remember that at home tests can’t be used to test for chlamydia in the throat or anus.


Chlamydia is treated with antibiotics, for about nine days.

Good to know

A chlamydia infection increases the risk of transmission of HIV and other STIs. There’s also a risk of damage to the ovaries especially, but also to the epididymides, which can affect the possibility of having biological children and increase the risk of ectopic pregnancy.

Chlamydia is subject to the communicable diseases act. That means that if you test positive for chlamydia the infection needs to be tracked to see who infected you and if you might have passed it on to others. You will therefore need to disclose who you have had sex with during the past months, but they won’t know who has given out their names.

There’s also a variation of chlamydia that is difficult to treat called LGV (Lymfogranuloma venereum). It’s reasonably uncommon but has become more common in recent years, especially among men who have sex with men that live with HIV. It’s transmitted in the same way as ordinary chlamydia, but can also cause sores on the genitals, in the throat or the anus, as well as swollen lymph nodes, bleeding and gastrointestinal symptoms. It may also be asymptomatic but still transmittable. LGV can be spotted if you test positive for chlamydia and have additional symptoms. The incubation period is long, and it may take a month before your lymph nodes get swollen. Sores can appear earlier. LGV is treated with double the course of antibiotics compared to regular chlamydia.

Mycoplasma genitalium is a relatively rare STI that resembles chlamydia, gives the same symptoms and is transmitted in the same way. If you show symptoms of chlamydia but still test negative, you can be tested for mycoplasma. Mycoplasma is treated with antibiotics.


Easily transmitted through different types of sex
Condom and lube gives good protection in intercourse
Sometimes asymptomatic
Testing and treatment is free A sample is taken from the vagina, penis, anus and throat, depending on what type of sex you’ve had
Treated with antibiotics

Gonorrhoea is a bacteria that is sexually transmitted. In 2019, about 3 200 cases were diagnosed in Sweden. About half of the reported cases concern transmission between men who have sex with men. Gonorrhoea has increased dramatically during the last years. Between 2016-2017, the number of cases increased by 42 %.

Gonorrhoea is an STI that is transmitted through contact with mucous membranes or through contact between bodily fluids and mucous membranes. It is easily transmitted. The infection can affect the genitalia, anus, eyes or throat. Most infections occur in the genitalia and anus, but there’s a great risk that the throat is infected. Gonorrhoea is most easily transmitted through vaginal and anal intercourse. The best way of lowering the risk of transmission is therefore to use a condom in anal and vaginal intercourse or to have sex without intercourse.

Gonorrhoea can also be transmitted in oral sex with a penis, and to reduce the risk you can use a condom. Both the person giving and receiving a blow job risks contracting gonorrhoea.

Gonorrhoea usually gives more symptoms than chlamydia, but not everybody who is infected is symptomatic. The symptoms usually occur within 2-10 days. The most common symptoms are discharge from the urethra and a stinging sensation when you urinate. An anal infection can lead to stinging and bleeding. Gonorrhoea of the throat is often asymptomatic.


A swab will be used to remove a sample for testing from the throat, urethra, cervix, anus or the inside of the eyelid, depending on where you were infected. Gonorrhoea of the urethra may be diagnosed with a urine sample, which is easier since swabbing may be perceived as painful. If the urine sample indicates gonorrhoea, you need to swab to analyse what type of gonorrhoea is present in order to give the right treatment.

Men who have sex with men often contract gonorrhoea of the throat or anus. Testing these areas of the body is therefore important.


Gonorrhoea is often treated with a single intramuscular injection of antibiotics or with tablets. The treatment can vary depending on what part of the body is affected and if the bacteria is resistant to any medications. Antibiotic-resistant gonorrhoea is a growing problem, and treatment is followed up to see if it has been successful.

Good to know

A gonorrhoea infection increases the risk of transmission of HIV and other STIs. There’s also a risk for damage mainly to the ovaries but also to the epididymides, and it may make it harder to have biological children and increase the risk of ectopic pregnancy.

Gonorrhoea is generally speaking an unusual STI, but it’s more common among men who have sex with men, especially men living with HIV. In later years, gonorrhoea has increased significantly among men who have sex with men. Gonorrhoea is subject to the communicable diseases act. That means that if you test positive for gonorrhoea the infection needs to be tracked to see who infected you and if you might have passed it on to others. You will therefore need to disclose who you have had sex with during the past months, but they won’t know who has given out their names.


Easily transmitted through different types of sex
Condom and lube are good, but not adequate, tools of protection in intercourse
Testing and treatment free
Relatively rare but can be serious if undetected and left untreated
Diagnosed with a blood test

Syphilis is a bacterial infection that was almost extinct in Sweden. In later years cases have increased, especially among men who have sex with men, even though very few still get infected. Close to 500 people are diagnosed with syphilis every year in Sweden (2019), of which most are men who have sex with men.

Syphilis is most often transmitted through contact between mucous membranes, but the infection can also be transmitted via the skin in areas with sores caused by the syphilis bacteria. Syphilis is easily transmitted in anal and vaginal intercourse without a condom and in oral sex with penis, vagina or anus. The risk of transmitting syphilis is greatest at the beginning of the infection. After that, the risk of transmission decreases. Syphilis is a systematic infection, which means that it affects your entire body.

Using a condom during intercourse is a good way of reducing the risk of transmission. Since syphilis is very contagious at the beginning of the infection, there’s a great risk of transmission when you have other types of sex or close contact. It’s therefore important to get tested regularly, especially if you belong to the group men who have sex with men, so that an infection can be detected and treated in time.

Syphilis is a serious illness and has different stages. The first stage lasts for three weeks up to three months. During that time you might notice a crater-like wound with hard edges that isn’t painful where the syphilis bacteria has entered the body. The wound can be located in an area where it can’t be seen, such as the mucous membrane of the anus. Swollen lymph nodes are also common. Even without treatment, the wound will heal in four to eight weeks.

The second stage begins after seven to ten weeks. You will commonly experience a fever, swollen lymph nodes and rashes on the body. The symptoms vary a lot and may mimic other infections. Some people are asymptomatic.


Syphilis is diagnosed through a blood test, but the entry wound can also be swabbed. The blood is taken from the bend of the arm or a finger.


Syphilis is cured with antibiotics. You will most often receive a shot of penicillin intramuscularly on two occasions one week apart. There are other treatment methods depending on how advanced the infection is and if you’re allergic to penicillin.

Good to know

Syphilis is relatively rare, but it is a serious illness. After many years, if undetected and untreated, it will enter into its third stage, which ultimately may lead to permanent damage to the nervous system and the organs of the body.


Easily transmitted through different types of sex, but also in other ways
Very common virus that most of us carry
Most often completely benign

Herpes is a virus that infects the neural pathways of the body. Most commonly affected are the lips and genitalia. Herpes is common and a large part of the population carries it, but not everyone is symptomatic. Herpes isn’t dangerous, but the blisters may be painful and bothersome. The blisters usually come in flares, which means you are periodically symptomatic, with total remission in between flares. Between flares, the virus lies dormant in the nerves of the mucous membranes. The blisters may come often or seldom, and some people get no blisters or only on one occasion. Many people experience blisters when they have a cold, are stressed or have a compromised immune system.

Herpes is transmitted through contact between mucous membranes or mucous membrane and skin, via saliva or other bodily fluids. Herpes can be transmitted in the absence of blisters, but the risk is smaller. The blisters often appear on or around the genitals, the anus and/or the mouth, on or close to the border between the mucous membranes and regular skin.

There are two types of herpes. Type 1 can affect both genitals and mouth, and type 2 affects the genitals but rarely the mouth. The most effective way to reduce the risk of transmission is to not let the infected mucous membrane come in contact with other mucous membranes when the virus is active. Before a flare, you usually feel an itching or stinging sensation on the skin where the blisters then appear. Avoid having oral sex if you have blisters in your mouth. Wearing a condom during intercourse reduces the risk of transmission somewhat.


Herpes is mainly diagnosed by looking for blisters. You can also test for antibodies in the blood, but it is uncommon. The incubation period for herpes is between two and 20 days.


Herpes can be treated with an anti-viral cream or, if your herpes is severe, anti-viral tablets.

Good to know

It’s estimated that between 50 to 90 percent of all adults carry herpes type 1, and between 15 and 30 percent carry herpes type 2.

The negative consequence of having herpes is mainly that the blisters hurt. Genital herpes can be transferred to a baby’s eyes during vaginal delivery, which can have serious implications. When you have a flare, the risk of contracting other STIs and HIV is increased. Herpes is a life-long infection. In rare cases, the virus can attack other parts of the body, which requires special care and treatment.

Some people who contract herpes get a primary infection with fever, pain and swollen lymph nodes. Subsequent flares are usually milder.


May be transmitted through different types of sex
Vaccine against hepatitis A and B
Treatment for hepatitis C

Hepatitis is a family of viruses. Sometimes, the skin and the whites of the eyes turn yellow, but not always. Other symptoms may be fever, fatigue and nausea. There are different kinds of hepatitis. Hepatitis A, B and C are the most common.

The different types of hepatitis are transmitted in different ways and are more or less difficult to contract.

Hepatitis A

Hepatitis A is transmitted through faeces and may sometimes be transmitted through sex, for example, oral sex in and around the anus. However, the virus is most commonly transmitted through contaminated food and water and therefore it isn’t classified as an STI. There’s a vaccine against hepatitis A. Hepatitis A usually resolves itself in about three months and no treatment is administered. If you’ve had hepatitis A you will have immunity for the rest of your life. Hepatitis A is especially common among men who have sex with men. If you’re a man who has sex with men it’s a good idea to get vaccinated. After two injections spaced out between six months, the body is immune to hepatitis A for 30 years.

Hepatitis B

Hepatitis B is transmitted through blood or during sex in the same way as HIV. Hepatitis B causes an infection of the liver. The virus is present in the whole body; in the blood, sperm and lubrication. The most effective way to reduce the risk of transmission is to use a condom in vaginal and anal intercourse and avoid sperm in the mouth. You can also use a condom in oral sex to further reduce the risk. Like hepatitis A, there’s a vaccine against hepatitis B.

About half of those infected by hepatitis B are asymptomatic. The symptoms are often nausea, diarrhoea, vomiting and stomach ache, as well as aching joints and muscles. After a while your urine may darken, your stool may become lighter and the skin and whites of your eyes may yellow. Hepatitis B often resolves itself, but about five percent develop chronic inflammation of the liver, which might lead to liver cancer. If you have had hepatitis B you will have immunity for the rest of your life.

For men who have sex with men, the vaccine against hepatitis B is free of charge. You need to take three shots over a period of time to be fully protected. There’s also a combination-vaccine that protects against both hepatitis A and B. You can get more information and get vaccinated at a healthcare centre or a vaccination clinic. All children born in Sweden are vaccinated against hepatitis B.

Hepatitis C

Hepatitis C is transmitted through blood, for example when sharing needles. Hepatitis C may be transmitted sexually, but the risk is often small.

Hepatitis C is often asymptomatic. People with acute hepatitis C often get yellow skin, experience nausea and have abdominal pain. About half of all hepatitis C cases lead to chronic inflammation of the liver, which may lead to cirrhosis and liver cancer.

There is an effective treatment for hepatitis C. The cost of medication is high, and not all patients with hepatitis C have access to care.

Hepatitis is diagnosed through a blood test.


Very common and easily transmitted
May cause genital warts/condyloma
May cause cancer of the cervix
Important to have a pap-smear if you have a uterus
Vaccine is now given to all children, regardless of gender

HPV (human papillomavirus) is very common and comes in different varieties. A majority of people with an active sex life will at some point contract HPV. Some types of HPV can cause genital warts that are also called condyloma. Other types can cause cellular anomalies that can lead to cancer. Many types of HPV heal on their own without leaving a trace.

HPV is transmitted through different types of sex and bodily contact. There are over 150 types of HPV and about 30 of them can infect the genitals, anus and tonsils. To reduce the risk of transmission you can use a condom when having vaginal and anal intercourse. If you have visible warts you should avoid having sex in places where the partner comes in contact with warts. It is difficult to minimise the transmission of HPV.

In people with a penis, the warts are usually on the foreskin, the glans or shaft, but they can also appear in the opening of the urethra. If you have a vagina, warts may form on the labia, in the urethra or on the vaginal vaults. They may also form deeper in the vagina and on the cervix, making them hard to detect. You can also get condyloma in and around the anus. HPV can also be transmitted to the mouth and throat. Warts can hurt, but most often they don’t.

In most types of HPV, you don’t develop warts. These types of HPV can cause cellular anomalies on and inside the cervix, the anus and throat, which can lead to cancer.

Testing and treatment

HPV is most commonly diagnosed by looking for potential warts. HPV that doesn’t cause warts is harder to diagnose. In Sweden, everybody between 23 and 60 years old with a female personal identity number is offered regular pap-smears. A pap-smear means taking a sample from inside the cervix inside the vagina with a small brush. The sample is then analysed for cellular anomalies so that it can be treated before developing into cancer.

Condyloma warts usually clear up by themselves after a few months and commonly don’t require treatment. If they are bothersome they may be treated with an ointment or cream. They can also be surgically removed.

Good to know

There are vaccines for HPV type 16 and 18 (which may cause cellular anomalies) and type 6 and 11 (which cause condyloma). Since 2020 the vaccine is offered to all children in fifth grade. The vaccine is most efficient if taken before you start having sex with others.

The HPV virus can be transmitted from vagina to vagina. It’s therefore important that everybody with a vagina, even those who have never had sex with someone with a penis, has regular pap-smears. If you have a vagina and are legally male you might not be summoned for a pap-smear, so you have to remember to make an appointment by yourself.

Bacterial Vaginosis

Bacterial vaginosis causes discharge from the vagina because of a change in the bacterial flora. The discharge is often runny and foul-smelling. It may itch and sting, but the condition is benign yet annoying. Bacterial vaginosis is very common, most people with a vagina get it at least once, and some many times. Bacterial vaginosis isn’t usually considered an STI since you most often get it without having had sex. The bacterial flora can change during menstruation if you have sex or for other reasons. However, there are studies that indicate that bacterial vaginosis can be sexually transmitted between vaginas. If you have bacterial vaginosis and have a steady partner who also has a vagina it might be a good idea for your partner to visit the gynaecologist for a check-up so that you can be treated at the same time. Bacterial vaginosis is usually treated with antibiotics.


A vaginal yeast infection, also known as candidiasis, is a common condition. A healthy vagina contains bacteria and some yeast cells. But when the balance of bacteria and yeast changes, the yeast cells can multiply. This causes intense itching, swelling and irritation. Yeast infections are harmless but annoying. Most people with a vagina experience it at some point, some multiple times. There’s both prescription and non-prescription medications you can use to treat it. Yeast infections are uncommon in people with a penis.

Urinary tract infections

Urinary tract infections are common among people with a vagina and are treated with antibiotics. People with a penis seldom get urinary tract infections since their urethra is usually longer. The most common symptom of a urinary tract infection is that it stings and hurts when you urinate. A urinary tract infection is not an STI, but you may get it after having had sex because the friction against the opening of the urethra may make it easier for bacteria to enter.