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Sexually transmitted infections (STI)

Sexually transmitted infections (or STIs) are infections that can be caught or passed on when you have unprotected sex, or close sexual contact, with another person who already has an STI.

Using a condom for all types of sex is the best way to avoid STIs and HIV. Vaccines can prevent certain STIs like genital warts and hepatitis B. Reducing the number of sexual partners you have and not mixing alcohol, drugs and sex also means you’re less likely to get infected.

STIs should not be diagnosed yourself by looking at pictures, because symptoms vary from person to person. Only a healthcare professional can diagnose an STI.

Find out more here about different STIs, their symptoms, testing and treatment options and how to protect yourself from them.

Next full review: 
25 November 2018
chlamydia in a human cell
Chlamydia often has no symptoms so test regularly if you are sexually active.
Herpes virus
Genital herpes causes sores that are really infectious. Get treated quickly.
Human papilloma virus (HPV)
Genital warts can be passed on by unprotected sex and skin-to-skin contact.
Gonorrhoeae bacteria
Gonorrhoea doesn't always have symptoms, but it can be treated with a short course of antibiotics.
Hepatitis virus
Hepatitis B is very infectious and can seriously affect your liver. It has flu-like symptoms.
Hepatitis C virus
Hepatitis C is also passed on through sharing dirty needles. Symptoms are not obvious.
Syphilis bacteria
Syphilis can be treated with antibiotics, but without treatment it can lead to serious health issues.
Trichomoniasis parasite
Trichomoniasis is caused by tiny parasites that can infect the vagina or urethra.
Hepatitis A viruses on colourful background
Hepatitis A is usually passed on through contaminated food and water, but it’s also a sexually transmitted infection. 
A single pubic louse on a hair
Pubic lice are passed on through close bodily contact with someone who has them and are usually sexually transmitted.
dgital image of HPV under microscope
There are over 100 different strains of HPV. Some strains of the virus are more risky than others.

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Last updated:
16 February 2017
Next full review:
25 November 2018