Toxoplasmosis affects birds and mammals worldwide. The incidence of human toxoplasmosis in any given area is influenced by diet and hygiene practices. For example, in areas where raw or rare meat is commonly eaten, as in France, toxoplasmosis can affect more than half of the population.¹ Eating infected meat is thought to cause about half of toxoplasmosis cases in the United States.²

Although nationwide toxoplasmosis statistics are not available, various studies reflect that infection with and immunity to Toxoplasma gondii varies widely across the United States.² For example, while a Denver study has reported a 3% rate of preexisting immunity among pregnant women, a 30% rate has been observed in Birmingham, Alabama.¹

Because American women are not routinely screened for toxoplasmosis during pregnancy, it is impossible to know how many pregnant women actually become infected. In the U.S., 1 to 10 newborns are infected in 10,000 births.³ This number is a fraction of the population of women who become infected during pregnancy. This is because many fetuses do not become infected along with their mothers.¹