Experts predict the next US states for Zika infections

(Credit: colleen/Flickr)

Nearly 400 non-travel-related Zika infections will occur in Florida before the end of the summer, according to new projections by biostatisticians.

In addition, they anticipate the virus will spread to several other Southeastern states with handfuls of cases projected to pop up from Texas to South Carolina and even Oklahoma.

The projections come weeks after the Florida Department of Health identified the nation’s first locally acquired cases of the Zika virus in Miami-Dade County. University of Florida researchers had already produced projections for other countries, which have experienced local Zika virus transmission for months—and in some cases, years.

Though the virus has been in South America for more than a year, some scientists doubted that it would ever come to the United States.

“It wasn’t clear at first whether mosquito densities were high enough to sustain an outbreak in the US,” says Ira Longini, a professor of biostatistics in the University of Florida College of Public Health and Health Professions and the College of Medicine.

Once the first cases of locally transmitted Zika fever were identified in Miami, however, Longini and his colleagues felt more comfortable publishing 2016 estimates projecting the number of locally transmitted cases that they expect will occur in Florida.

Zika in Miami was ‘just a matter of time’

The model projects 395 Zika infections in Florida by Septemer 15 due to local transmission and 79 symptomatic cases by the same date. In addition, they forecast that a median of eight of the infections will be in pregnant women during their first trimester.

Other states expected to see locally acquired Zika are below, followed by the number of locally acquired cases and the number of symptomatic cases:

  • Alabama: 11, 2
  • Arkansas: 3, 1
  • Georgia: 6, 1
  • Louisiana: 4, 1
  • Mississippi: 10, 2
  • Oklahoma: 12, 2
  • South Carolina: 16, 3
  • Texas: 5, 1

While many researchers have performed retrospective analyses of Zika infection outcomes using data from Brazil and elsewhere in Latin America, none to date have involved prospective cohorts. This cohort will allow investigators to follow pregnant mothers through time, measuring the pregnancy outcomes of those who were likely infected in the in the first trimester of their pregnancy.

The results of the research will help Longini and others further codify the range of birth defects that fall under congenital Zika syndrome, as well as the likelihood of microcephaly and other birth defects.

As many of the prospective mothers began their pregnancies during late 2015 and early 2016, Longini expects to begin learning about their pregnancy outcomes in the fall.

Zika’s first wave could infect 1.65 million childbearing women

Much of the analysis presented on the website appeared last July in bioRxiv.

Longini, a senior researcher at the Emerging Pathogens Institute, worked with researchers at Northeastern University, the University of Washington, and several other institutions to produce a website showing how Zika virus has spread through Mexico, the Caribbean, and Central and South America, and projecting how it might spread in the future.

“In Colombia, we’re trying to estimate the proportion of women infected in the first trimester who get microcephaly and other birth defects,” Longini says. An article appears in Eurosurveillance on Zika epidemiology and transmissibility in Colombia.

The researchers are working with the Colombia National Institute of Health, which has assembled a cohort of 15,000 pregnant women who are either known to have been infected with Zika virus while pregnant or who suspect they were infected.

“That’s the largest cohort in all of Latin America,” says Diana Patricia Rojas, a third-year graduate student in epidemiology at the University of Florida. “It will give very good information about the exact proportion of pregnant women infected with Zika that can develop birth defects.”

Source: University of Florida