By Carol Christian | November 12, 2013 | Updated: May 19, 2014 | Houston Chronicle

The number of people contracting the warm-water bacteria that can cause illnesses ranging from tummy upsets to potentially fatal skin lesions has increased in recent years, according to federal data.

Records kept by the U.S. Centers for Disease Control and Prevention show that the number of cases of Vibriosis nearly doubled between 2008 and 2012 - rising from 588 to 1,111.

Vibriosis includes "Vibrio vulnificus," the bacteria commonly dubbed "flesh-eating." It's rare but tends to be underreported, the CDC says on its website.

The CDC data on vibriosis includes all vibrio species except cholera, so it's unclear how much of the increase in the past five years is due to infection by the flesh-eating bacteria that can cause death.

One researcher who studies Vibrio vulnificus found it highly concentrated in tar balls that appeared along the Gulf Coast after the 2010 BP Deepwater Horizon oil spill.

Covadonga Arias, a professor of microbial genomics at Auburn University in Alabama, found that Vibrio vulnificus was 10 times higher in tar balls than in sand and up to 10 times higher than in seawater.

Her research, conducted with colleagues Zhen Tao and Stephen Bullard, was published Nov. 23, 2011, in EcoHealth.

It marked the first analysis of bacteria found on the large amounts of "weathered oil" (such as tar balls) from the BP Deepwater Horizon spill that ended up on the shoreline, the researchers said.

For the study, samples of sand, seawater and tar balls were collected from July through October, 2010, from a beach in Alabama and two beaches in Mississippi.

The authors said their findings have epidemological relevance since many people have stepped on tar balls or picked them up on the beach.

However, in a June 2012 letter to BP, Dr. Thomas Miller, the deputy director for medical affairs at the AlabamaDepartment of Public Health stated, "There is no epidemiological evidence to indicate increased rates of Vv (Vibriosis vulnificus) infections. Analysis of current and previous years' Vv case numbers indicates there is no increase in the number of cases for years 2010 - 2012."

In response to the EcoHealth article by Arias, Tao and Bullard, the U.S. Coast Guard's on-scene coordinator for the oil spill management asked the National Oceanic and Atmospheric Administration to review the risk of Vibrio vulnificus infection due to tar ball exposure.

NOAA's review, released in June 2012, noted that Vibrio infections had risen "dramatically" in recent years, with a 78 percent increase between 1996 and 2006.

In regard to the paper by Tao, Aris and Bullard, the NOAA report said, "It is not surprising to find high levels of bacteria associated with these oil sources, although why V. vulnificus is present at such high levels is an intriguing question....The implications to public health also remain unclear."

The NOAA report also stated that more research on a wider variety of shoreline types and other possibly contributing factors is necessary before concluding that tar balls contaminated with V. vulnificus represent a spill-related threat to public welfare.

NOAA scientists then asked the Centers for Disease Control whether CDC surveillance data showed changes in the frequency of V. vulnificus infection that might correlate with the oil spill.

In a July 2012 memo, the CDC stated that a review of Vibriosis surveillance data showed no evidence of such an increase.

"Incidence rates of vibriosis in the year before (2009) and the year after (2010) the Deepwater Horizon oil spill were compared and no significant difference in incidence was found," the CDC memo stated.

BP spokesman Jason Ryan said Nov. 11 in an emailed statement: "The Auburn study does not support a conclusion that tar balls may represent a new or important route of human exposure for Vibrio infection, or that the detection of Vibrio in tar balls would impact the overall public health risk, since there are other far more common sources of Vibrio, such as seawater and oysters.

"This is a naturally occurring bacteria found in the Gulf of Mexico. Neither the Alabama Department of Health nor the Centers for Disease Control have reported any significant increase in cases in the last three years and no individual case of vibrio infection has been linked to tar ball exposure."

While there is no proof that tar balls can infect humans, Arias said it's a concern because the bacteria concentration is so high in the samples her team studied.

"At a concentration as high as 1 million Vibrio vulnificus cells/g (per gram) of tar ball, I think the potential risk is there," she said by email.

Concentrations in oysters and seawater are typically much lower, she said.

To prove that tar balls can infect humans will require more study, which takes a lot of money, she said.