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What are sexually transmitted infections?

What are sexually transmitted infections?

It’s probably not the first thing that comes to mind, but if you are not careful, chances are you will be exposed to any one of more than 30 bacteria, viruses or parasites that can take advantage of you when you have sex. As the name suggests, a sexually transmitted infection (STI), sometimes called a sexually transmitted disease (STD), is an infection that can be passed on to another person during vaginal, anal or oral sex. Of the 30 or so, eight STIs are particularly common and cause most sexually transmitted illnesses:
CurableTreatable but incurable
Chlamydia (bacteria)Genital herpes (virus)
Gonorrhea (bacteria)Hepatitis B (virus)
Syphilis (bacteria)HIV (Human Immunodeficiency Virus)
Trichomoniasis (parasite)HPV (Human Papilomavirus)

How your body keeps germs out

Usually, the millions of germs we come into contact with everyday don’t harm us. Our skin, a thick dry layer that covers the outside of our bodies, and mucous membranes (thinner, moist layers that line the cavities of our bodies) are very effective at keeping them out. Although mucous membranes are much thinner than skin and less of a physical barrier to infection, the slippery fluid they produce (mucus) not only stops us from drying out, but also contains chemicals that kill germs and help protect us against infection.

What can go wrong?

Although your skin and mucous membranes are well equipped to keep infections at bay, germs can overpower these defences and cause an infection. Because the mucous membranes are thinner than skin, they are more vulnerable to microbes, which can sometimes get through. Once inside, the microbes multiply inside your body and get into your body fluids including your blood, semen, and vaginal fluids. During sex, these fluids often mix together and get spread in and around your genitals, anus, or mouth. This means the microbes are perfectly positioned to cross the mucous membranes of the vagina, penis, urethra, rectum, mouth, or throat from one partner to the other and vice versa. It’s also possible for some types of microbes that cause STIs to enter your body through tiny cuts or lesions on your skin, or even through your eyes.


STIs often don’t cause any signs or symptoms, so it is common to be infected and not know it. That said, if you do get symptoms they will typically include one or more of the following:
  • abnormal discharge from your penis or vagina, itching, or general irritation
  • a burning feeling when you urinate
  • a rash or sores on or around your genitals
  • unusual bleeding not associated with your period
  • pain and swelling in your testicles
If left untreated, curable and incurable STIs may persist for years and can cause all sorts of severe and potentially life threatening health problems.
Chlamydia, gonorrhea, syphilis, and trichomoniasis: it doesn’t matter whether you are male or female, these STIs can make you sterile. However, if you are a woman, you are likely to suffer more severely. Around 40% of women with untreated chlamydia or gonorrhea will develop pelvic inflammatory disease and one in four of these will become infertile. If you are already pregnant and get one or other of these STIs, there’s a high risk that you will pass it on to your baby, which depending on the infection can cause premature birth, stillbirth, and blindness in the newborn.
Herpes: if you get symptoms, the first episode of genital herpes is usually the worst and this may or may not be followed by a flare up every now and again for many years. As with many viral infections, you may get flu-like symptoms during the initial episode in addition to sores, blisters, pain, and itching.
Hepatitis B and HIV: both of these viruses may also cause flu-like symptoms a few weeks after you get infected. Most people with hepatitis B feel better within a few weeks and will get rid of the virus completely in a few months. For about one in ten people though, it becomes chronic and progressively damages the liver, causing severe nausea, vomiting and jaundice, and sometimes liver cancer.2 If you get HIV, on the other hand, you have it for life. HIV attacks your white blood cells, which reduces your body’s ability to fight off other infections. If you don’t get treatment, usually after an average of 10 to 12 years with few or no symptoms, you will develop AIDS. This is a life-threatening illness with many different symptoms caused by multiple infections by organisms that are normally harmless, but that may be very dangerous when up against a damaged immune system.
HPV: this virus comes in many different forms. Some of these forms can cause changes to your cervix that lead to cervical cancer, and others cause genital warts, or more rarely anal cancer. There are usually no symptoms when you get infected, but if you go on to develop cervical cancer, the most common signs are abnormal vaginal bleeding and discharge, and pelvic pain. Genital warts can affect both men and women. They are typically small, but you may notice these small grey coloured swellings that look a bit like cauliflower, in and around your genitals. Warts can also develop in your mouth or throat if you have oral sex with an infected partner.

What puts you at risk of an STI?

  • You are at risk of getting an STI if you are sexually intimate with your partner or partners when they have genital sores, a rash, or a discharge of any kind, or if they mention any other symptoms that may occur when you have an STI.
  • It is very common to have an STI but no symptoms, so it’s possible that your sex partner or partners won’t know if they have one or not, and you won’t be able to tell. In almost all circumstances, having unprotected sex (not using a condom) puts you at risk of getting an STI.
  • Having an STI can make it much more likely that you will get HIV when you have sex with an HIV infected partner; for example, having syphilis makes it three times more likely you will catch HIV.1

How likely are you to get an STI?

Every day around 1 million people get an STI. You have about equal chance of getting one whether you are male or female. Around half of these new infections are chlamydia, gonorrhoea, syphilis, and trichomoniasis - all of which can be cured.1 More than 500 million people have herpes, and almost 3 million women have HPV. The chances of getting an STI vary in different parts of the world, but no matter where you live, you are more likely to get one if you are sexually active and under 25 years old. Because it is so often impossible to know if someone has an STI, and exposure to just a small amount of microbes can cause an infection, it is wise to assume there is a chance you could get infected whenever you have unprotected sex.

How you can prevent an STI?

  • Use a condom
    • unless you’re sure that you and your partner only have sex with each other and you have both tested negative for STIs, you are at risk of getting an STI if you don’t use a condom. Male and female condoms are very effective at preventing you from getting an STI.
  • Don’t have sex
    • avoid having sex if your partner or partners show any signs or symptoms of an STI.
  • Get tested
    • If you are about to start having sex, or starting a new relationship, you and your partner should get tested for STIs before you do it. Then get tested annually or more frequently if you think you might have been infected.
  • Don’t share
    • some microbes can live outside of the body on towels or underclothing for days.
  • Get vaccinated
    • the hepatitis B vaccine and HPV vaccines can help protect you against these STIs.

How are STIs treated?

If you think you might have an STI or suspect you have been exposed to one during sex with an infected partner, the earlier you get treatment the better. Once you have been properly diagnosed, your doctor will be able to select from a variety of treatments.
Chlamydia, gonorrhea, syphilis, and trichomoniasis - these STIs are best treated with antibiotics, and if treated early, can generally be cured. However, it is very important that your sex partner or partners also get treatment so that you don’t reinfect each other or infect anyone else.
Herpes and HIV - these STIs are best treated with antiviral medicines. These medicines are not a cure, but they can reduce the severity of the disease so that you are as healthy as you can be.
Hepatitis B - there is no cure for chronic hepatitis B, but it can be treated with medicines that help your immune system fight it, and with antiviral medicines. Whether or not you need to take these depends upon how active the virus is inside your body, and how much damage it is doing to your liver, things your doctor will decide. There is a vaccine available that will protect you from getting hepatitis B, so if you were not vaccinated as a child, and are sexually active, look into getting this shot.
HPV - there is no treatment for HPV itself, but genital warts and cervical problems can be treated if necessary. There is an HPV vaccine available in many countries that helps prevent cervical cancer, anal cancer, and genital warts that is generally made available to girls and young women, and sometimes to boys and young men.

Consider the following:

It is very important to get tested if you think you might have an STI. As well as making sure you are prescribed the medicine you need to treat or cure it, doctors and nurses can help you in other ways. How might that be? You need to take the medicine exactly as the doctor tells you for it to work properly. The medical staff may be able to make it easier for you by giving you a single dose that you can take there and then, or if you need more than one dose, they can give you a written treatment plan to follow. In addition to this, they can often help you let your sexual partner or partners know that there’s a chance they may also have an STI, so that they can get tested and treated too, if necessary.

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