Caused by a roundworm spread by dog feces that typically infects children playing on the ground, 14 percent of the U.S. population was found to have been exposed to it in a CDC study, using data collected between 1988 and 1994.
There may be a link between toxocariasis and asthma, though past studies have been inconclusive. There is a relationship, say doctors, but it may simply be that both happen in poor living conditions.
Hotez believes that better surveillance of toxocariasis might lead to a drop in asthma cases, as drugs are available to treat the roundworm, distinct from the medications to treat asthma. Doctors may currently be treating asthma symptoms rather than the cause, he said.
"It can cause symptoms as the larva are migrating and enter the lungs," said Susan Montgomery, a researcher with the CDC's section on parasitic diseases. But, she said, "[The] specific syndrome of asthma has not been causally linked to toxocariasis."
But others are less sure.
"Toxocariasis doesn't cause a lot of clinical disease," said Dr. Robert Tolan, Jr., chief of the division of allergy, immunology and infectious diseases at the Children's Hospital at Saint Peter's University Hospital and a clinical associate professor of pediatrics at the Drexel University College of Medicine in Philadelphia.
Despite a high infection rate, Tolan said the worst cases, such as where a child develops a vision problem because of a worm infection, might only happen once every 10 years or so.
He said that he feels other infections, such as Chagas, may be more pressing to study because of the severe illnesses they can cause.
Montgomery expressed some optimism that toxocariasis infection may have dropped since the last survey, mostly through greater efforts at getting animals de-wormed.
"It's possible all of that good veterinary care is reducing the human risk of toxocariasis," she said.
But she said the survey itself would still be important.
"We suspect a portion of them did and may have pretty severe illness," she said of the millions that had been infected. "It is a health disparity and one that we feel is important to address."