What percentage of the population is positive for Toxoplasma gondii IgG antibodies and cytomegalovirus IgG antibodies?

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Seroprevalence of Toxoplasma gondii and Cytomegalovirus IgG Antibodies

In the United States, approximately 12.4% of the population over age 6 is positive for Toxoplasma gondii IgG antibodies, while CMV IgG seroprevalence is substantially higher at approximately 60-98% depending on the population studied.

Toxoplasma gondii IgG Seroprevalence

The most recent U.S. data from NHANES 2009-2010 shows:

  • Overall age-adjusted seroprevalence: 12.4% (95% CI: 11.1-13.7%) in people older than 6 years 1
  • The unadjusted rate was 13.2% (95% CI: 11.8-14.5%)
  • Women of childbearing age (15-44 years): 9.1% (95% CI: 7.2-11.1%) 1

Important Population Variations:

  • Foreign-born individuals: 25.1% vs. U.S.-born: 9.6% 1
  • Hispanic background: 15.8% vs. non-Hispanic white: 10.2% 1
  • Children on farms: 18% vs. non-farm children: 4% 1

The seroprevalence has been declining over the past two decades - among U.S.-born women of childbearing age, rates dropped from 13% (1988-1994) to 8% (1999-2004) to 6% (2009-2010) 1.

Cytomegalovirus IgG Seroprevalence

CMV IgG antibodies are far more prevalent than Toxoplasma:

  • Overall population: 60.8% in a large Danish study 2
  • Pregnant women studies show 96.3-99.7% seroprevalence 3, 4, 5
  • A Turkish study found 98.2% CMV IgG positivity in women of childbearing age 5
  • An Iranian study reported 99.7% CMV IgG positivity 4

Regional Variations:

Recent studies from different regions consistently show very high CMV IgG seroprevalence:

  • Turkey (2020): 98.2% 5
  • Iran (2022): 99.7% 4
  • Brazil (2023): 96.3% 3
  • China (2025): 97.5% 6

Clinical Significance

Most U.S. women of childbearing age (approximately 91%) remain susceptible to Toxoplasma infection, which poses risk for congenital toxoplasmosis if primary infection occurs during pregnancy 1. In contrast, the vast majority of the population has been exposed to CMV, though reactivation during pregnancy can still cause congenital infection.

The stark difference between these two pathogens - with Toxoplasma affecting roughly 1 in 8 Americans versus CMV affecting 6-10 in 10 - has important implications for screening strategies and counseling about infection prevention during pregnancy.

References

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