Trends in congenital syphilis transmission rates raise concerns

Congenital syphilis transmission rates nearly doubled among infants born in the southern part of the United States between 2005 and 2008, but remained relatively stable overall, according to CDC data published online today.

CDC researchers noted that the annual number of cases of congenital syphilis transmission decreased from 432 to 339 between 2003 and 2005, but then increased to 431 in 2008. The incidence rate per 100,000 live births decreased from 10.6 cases in 2003 to 8.2 cases in 2005, but then increased to 10.1 cases in 2008.

Increases in the number of cases of congenital syphilis were observed between 2005 and 2008 in infants born to white women (31 to 65), black women (156 to 215), women in the South (148 to 253) and women in the Northeast (28 to 37).

Congenital syphilis transmission rates per 100,000 population remained relatively stable among infants born to Hispanic, Asian Pacific Islander and American Indian/Alaska Native women.

A 38% increase in primary and secondary syphilis rates among all females older than 10 years was observed between 2004 and 2007, from 0.8 to 1.1 per 100,000 live births. There were 1.5 cases of primary and secondary syphilis per 100,000 live births among all women in the United States in 2008.

In 2008, 50% of congenital syphilis cases in the United States were in infants born to black mothers; infants of Hispanic mothers comprised 31% cases and infants of white mothers comprised 15%.

More than a quarter of all women (125 of 431) who delivered infants with congenital syphilis in 2008 did not receive prenatal care.

Data from 2008 indicated that among the 276 cases in which the mother received prenatal care, 75 mothers received an initial syphilis screening less than or equal to 30 days before delivery. In 2008, there were 67 mothers who were screened more than 30 days before delivery and received a positive result but were untreated. These data were similar to those reported for 2003 and 2005.

The case-fatality ratio of infants with congenital syphilis who were stillborn decreased from 7.6% in 2003 to 6.5% in 2008.

The increase in primary and secondary syphilis rates between 2005 and 2008 may indicate that larger increases in congenital syphilis rates could occur in 2009 and in future years, according to the researchers.

Su JR. MMWR. 2010. 59:413-417.