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STIs affect people of all backgrounds and income levels. But nearly 50 out of 100 STI cases in the U.S. happen in people younger than age 25. 
       
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STIs are on the rise, possibly due to more sexually active people who have multiple sex partners during their lives. 
       
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Many STIs cause no symptoms at first. And many STI symptoms may be confused with those of other diseases not spread by sex, especially in people with a uterus. Even symptomless STIs can be contagious. They can later cause long-term (chronic) or serious health problems.  
       
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People with a uterus suffer more frequent and severe symptoms from STIs: 
        
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Some STIs can spread into the uterus and fallopian tubes and cause PID. This can lead to both infertility and ectopic (tubal) pregnancy. 
           
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Some strains of HPV infection may also be linked to cervical cancer. In all people, these strains may cause anal, head, and neck cancer. 
           
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STIs can be passed from a birthing parent to their baby before or during birth. Some newborn infections may be successfully treated. Others may cause a baby to be permanently disabled or even die. 
           
        
       
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Once diagnosed, many STIs can be successfully treated. Some STIs, such as herpes, can't be completely cured and may happen again. But each recurrence can be prevented or treated. 
       
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Key ways to prevent transmission of HIV infection include PEP within 72 hours of exposure and PrEP to prevent transmission if there is ongoing risk. Also make sure that HIV-positive partners are under treatment and have their virus under control.