CDC Underestimating US Zika Cases: Study

New reports that 14 people in Florida have been infected with the Zika virus through local mosquito transmission have intensified concerns about outbreaks in the U.S. But a new study says the number of  Zika cases confirmed by health officials vastly underestimates the actual infections.

The new study, led by Northeastern University professor Alessandro Vespignani, estimates the actual number of U.S. Zika cases is 25 times greater than the figure reported by the Centers for Disease Control and Prevention.

The reason: 80 percent of infected people never have symptoms or see a doctor.

"We don't project very large outbreaks in the continental U.S.," noted Vespignani, whose lab has been running the simulations of likely Zika infection transmission. "But there is a certain set of countries in the Americas that has the right mosquitoes, the right weather, and the right socioeconomic conditions for major outbreaks."

He explained that those conditions include lack of air conditioning, poor sanitation, and little access to Zika-precaution education on preventative measures such as removal of standing water, which attracts mosquitoes.

To reach its conclusions, Vespignani’s team of 14 researchers used computer models that integrate sociodemographic and travel data of target populations along with simulations of infection transmission among millions of individuals.

"Even of those with symptoms, probably only one-third will go to the doctor and get diagnosed," he said

For this reason, he said the number of travel- associated cases of Zika in the U.S. reported by the CDC “may be just the tip of the iceberg.”

His team projected, for instance, that as of June 15 there were nearly 30,000 cases of travel- related Zika in the U.S. — a number 25 times greater than that reported by the CDC on the same date.

The discrepancy results from the difference between reported cases of the mosquito- borne virus — those actually diagnosed and reported to the CDC — and those that are missed, but estimated by Vespignani’s computer models.