What Is A Chlamydia Infection?

How to Understand this Disease

Chlamydia' usually refers to the sexually transmitted infection (STI) which a bacterial infection passed between people during (usually unprotected) sex.

Having said that, chlamydia is a bit more complicated, with different types and consequences, it's important to know how to protect yourself from it.

What Exactly is Chlamydia?

In fact, when we talk about ‘chlamydia’, most often we are talking about a specific type of chlamydia known as Chlamydia trachomatis, which is a sexually transmitted infection (STI).

Different types of chlamydia – ‘chlamydia’ is actually the name for a family of organisms, each with a slightly different genetic appearance or subtype. Chlamydia A-C affects the eye, chlamydia D - K affects the genitalia and chlamydia L causes a condition known as lymphogranuloma venereum (LGV).

Where chlamydia lives:

  • Genital chlamydia:
  • If you’re a man – chlamydia may infect the urethra (the tube which passes down the length of the penile shaft), the bladder, the prostate gland, and the testes
  • If you’re a woman – chlamydia may infect the cervix (the neck of the womb), the endometrium (the womb lining) and the fallopian tubes and ovaries, as well as the bladder. It may also affect the peritoneum (the membrane which lines the abdominal cavity) and the liver
  • Other parts of the body:
  • Chlamydial conjunctivitis (eye chlamydia) – this occurs when chlamydia infects the eye. In third world countries, this is the most common cause of blindness. Chlamydial conjunctivitis is most common in babies – a newborn baby becomes infected during childbirth from passage through an infected birth canal. However chlamydia can cause conjunctivitis in adults too
  • Chlamydia pneumoniae – this occurs most often in small babies, or in people with a poorly functioning immune system
  • Chlamydial arthritis – this may develop, sometimes in conjunction with genital symptoms (urethritis in men) and eye symptoms (conjunctivitis)
  • Lymphogranuloma venereum (LGV) – This is also a different subtype of chlamydia, which infects the genitalia to cause large painful, groin abscesses. This is very rare in the UK

How is STI chlamydia passed on? – sex. Chlamydia is a sexually transmitted infection. If you are diagnosed with chlamydia, this means the infection has been acquired from a sexual encounter with an infected person. Chlamydia may be transmitted by having these type of sex – oral, vaginal, or anal. STI chlamydia can be detected at any of the following sites:

  • In the mouth
  • In the vagina/on the cervix
  • In the urethra
  • In the rectum

What exactly passes on chlamydia – the infection spreads mostly due to the bacteria within body fluids, for example semen, and vaginal/cervical secretions. Chlamydial organisms may be present in pre-ejaculatory fluids (precum). This means even just sexual touching, or any delay in applying a condom, could result in the infection being passed on. This means you could still become infected even if ejaculation does not occur, and even if you do use a condom properly.

How is the diagnosis of chlamydia usually made?

If you’re a woman – by taking a vulvo-vaginal chlamydia swab. You may be asked to do this yourself. A thin, cotton tipped swab is inserted into the vagina around 2-3 cm and rotated for around 20 seconds pressing firmly on the vaginal wall. The swab is then placed into the plastic inserter and the tip is broken off for transport. This is not painful

If you’re a man – by a first pass chlamydia urine test. You must not have passed urine for 2 hours (1 hour minimum) before providing the sample. When you do the specimen you need to provide the first part of the stream

It is possible to test women with a first pass urine test, and for a males to have a urethral swab taken. But in clinical practice, this is less common. If you attend a clinic, you will be advised about this.

How Serious is Chlamydia?

Risks are more serious if you don’t get treated – 20-54% of chlamydia cases will resolve within one year without treatment. Of those who do not clear the infection spontaneously, they are more likely to go on to develop symptoms of chlamydia. Although chlamydia can go away on it’s own, the most serious consequence of untreated infection is PID, and specifically tubal infection – salpingitis. The risk of PID from untreated chlamydia is higher at 17.1%, and risk of salpingitis is 7.3%.

What damage does chlamydia do? – while chlamydial organisms are multiplying with the genital tract, there is damage to the host (your) cell tissues (insides of your genitals). Cell damage causes inflammation within the tissue – that is redness, swelling, and sometime bleeding. The end result of this process may be scar tissue formation and this is why chlamydia can cause infertility (problems having children) from your tubes not working properly or getting blocked.

In women aged 16-44, untreated chlamydial infection accounts for:

20% cases of PID

4.9% ectopic pregnancy

29% tubal factor infertility

Can it be fatal or cause permanent disability? – ectopic pregnancy is a very serious consequence of chlamydia, which can be life-threatening. An ectopic pregnancy occurs if a pregnancy develops not inside the womb, but inside the Fallopian tube. If the tube bursts, there may be severe internal bleeding, which can be fatal. Emergency surgery is needed. Sometimes other organs are involved such as bowel or bladder.

Does chlamydia affect your fertility? – yes it can. Chlamydia can cause inflammation and scarring within the female tissues in the pelvis. The Fallopian tubes may become filled with fluid, blood, or pus, and this means an egg cannot pass through the tube after ovulation.

Does Chlamydia Affect Your Periods?

Yes it can – chlamydia infects the genital tract, and this includes the uterus (womb), the cervix (the neck of the womb) and sometimes the Fallopian tubes and ovaries. Inflammation within the genital tract gives rise to a variety of symptoms, including sometimes abnormal/unexpected vaginal bleeding.

Chlamydia may cause:

  • Heavier periods
  • Bleeding in between periods or bleeding during or after sexual intercourse
  • Irregular bleeding – this is especially common in women using hormonal contraception
  • Inflammation on the cervix, known as ‘cervicitis’

Do you still need birth control if you have chlamydia? – you are advised not to have sex while being treated for chlamydia for a minimum of 7 days. If you do have sex, you should continue your usual form of contraception while on treatment. There is no need to stop the contraceptive Pill for example.

Is it definitely chlamydia causing my period changes? – even if you know for a fact you have chlamydia, there are still other causes of period changes that you should consider, including:

  • Pregnancy – miscarriage, ectopic pregnancy
  • Infections – chlamydia and other STI’s
  • Pathology – cervical polyps, cervicitis, cervical erosions/ectropion, cervical cancer (rare), endometrial polyps, endometrial hyperplasia, endometrial cancer (rare) ovarian tumours
  • Systemic disease – polycystic ovarian syndrome (PCOS), hypothyroidism, extreme weight loss or weight gain, severe stress, pituitary disease (rare), premature menopause, haemochromatosis and other rare conditions
  • Contraceptive side effects

Remember that, most often periods will vary or an occasional period can be missed with no sinister cause. It is always wise to do a pregnancy test early on to be sure.

Does Chlamydia go Away on its Own?

How long does a chlamydia infection last if untreated? – 20-54% of chlamydia cases will go away on their own after one year without treatment. It’s not a good idea to wait and see if the problem solves itself because the longer you have the infection, the more likely it is you get complications, including the serious ones.

Will anything make it go away faster? – nothing will be as reliable as diagnosing and treating chlamydia. This is the best way to get rid of it and it can be cured by a simple course of antibiotics. When using treatment, it’s important to follow all the advice about treatment carefully to be sure the infection has been properly treated.

The most common antibiotic for chlamydia is doxycycline 100mg twice a day for 7 days. Chlamydia treatment is important because it helps reduce your risk of serious side effects and means you won’t be infectious to other people afterwards.

Once it goes away after treatment – will it come back? – once the infection has been treated successfully, you will have been cured and won’t still be infected (unlike some other STIs like herpes for example). It is possible to get chlamydia again, but only if you are exposed again to the infection through having sex with another sexual partner who has chlamydia. The risks of negative outcomes from chlamydia increase with the number of times you become infected. If you do have chlamydia, it’s very important you try hard not to get it again.

Can You Become Immune to Chlamydia?

Unfortunately, you cannot become immune to chlamydia – a previous episode of chlamydia does not give any long term protection to the infection. Repeated episodes of chlamydial infection increase your chance of unpleasant long-term outcomes from the infection. There is also no vaccine because of the way chlamydia has so many subtypes and infects parts of the body that vaccines are less useful for protecting.

Why isn’t it normal to get immunity to chlamydia? – this is partly because the area chlamydia inhabits inside the genitals is not easy for the immune system to reach. All the white blood cells responsible for fighting off disease have limited access there so it’s harder for them to clear a bacterial infection the way they would in other parts of the body. Chlamydia are also hard for the immune system to recognise properly, which is important for the immune system to work properly.

How can you prevent chlamydia long-term? – until a vaccine is developed, the best thing to do is to try to reduce your risk through good sexual health:

  • Always use a condom correctly and consistently with any new sexual partner
  • Get tested for chlamydia, especially if you are aged 25 or under and/or have any risk factors
  • Keep being tested, preferably before you have unprotected sex with a new partner. Avoid overlapping partners
  • If you do test positive to chlamydia, follow all the advice about treatment very carefully


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