Its infectivity is exemplified by the fact that an individual inoculated with only 57 organisms has a 50% chance of being infected. Most new cases in the United States (60%) occur in men who have sex with men; and in this population 20% of syphilis cases were due to oral sex alone. Syphilis can be transmitted by blood products, but the risk is low due to screening of donated blood in many countries. The risk of transmission from sharing needles appears to be limited.It is not generally possible to contract syphilis through toilet seats, daily activities, hot tubs, or sharing eating utensils or clothing. This is mainly because the bacteria die very quickly outside of the body, making transmission by objects extremely difficult. Diagnosis
Syphilis is difficult to diagnose clinically during early infection. Confirmation is either via blood tests or direct visual inspection using dark field microscopy. Blood tests are more commonly used, as they are easier to perform. Diagnostic tests are unable to distinguish between the stages of the disease. Blood tests
Blood tests are divided into nontreponemal and treponemal tests.Nontreponemal tests are used initially, and include venereal disease research laboratory (VDRL) and rapid plasma reagin (RPR) tests. False positives on the nontreponemal tests can occur with some viral infections, such as varicella (chickenpox) and measles.
The Centers for Disease Control and Prevention (CDC) states, "Correct and consistent use of latex condoms can reduce the risk of syphilis only when the infected area or site of potential exposure is protected. However, a syphilis sore outside of the area covered by a latex condom can still allow transmission, so caution should be exercised even when using a condom. "Abstinence from intimate physical contact with an infected person is effective at reducing the transmission of syphilis. The CDC states, "The surest way to avoid transmission of sexually transmitted diseases, including syphilis, is to abstain from sexual contact or to be in a long-term mutually monogamous relationship with a partner who has been tested and is known to be uninfected." Congenital disease
Congenital syphilis in the newborn can be prevented by screening mothers during early pregnancy and treating those who are infected. The United States Preventive Services Task Force (USPSTF) strongly recommends universal screening of all pregnant women, while the World Health Organization (WHO) recommends all women be tested at their first antenatal visit and again in the third trimester. If they are positive, it is recommended their partners also be treated. Congenital syphilis is still common in the developing world, as many women do not receive antenatal care at all, and the antenatal care others receive does not include screening. It still occasionally occurs in the developed world, as those most likely to acquire syphilis are least likely to receive care during pregnancy.