(CNN) More than one million new cases of four sexually transmitted infections (STIs) are contracted every day, according to figures released Thursday by the World Health Organization (WHO).

The four infections are chlamydia, gonorrhea, trichomoniasis (or "trich") and syphilis, with the WHO finding on average that one in every 25 people globally has at least one of these STIs, sometimes known as STDs.

"These infections indicate people are taking risks with their health, with their sexuality and with their reproductive health," said Dr. Melanie Taylor, lead author of the report and medical epidemiologist at the WHO department of Reproductive Health and Research.

The WHO said that there are more than 376 million new cases annually, with the figures representing cases, not individuals, explained Taylor, as people can be infected with multiple STIs, or can become re-infected within a year with one or more STIs.

STIs are transmitted through unprotected vaginal, anal and oral sex. Some can be passed from mother to child during pregnancy or childbirth -- notably chlamydia, gonorrhea and syphilis. Syphilis can also be transmitted by coming into contact with infected blood.

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