Hurricanes, infectious disease and public health

In the first study ever to evaluate urban sediment after Hurricanes Katrina and Rita, scientists from the University of Miami Rosenstiel School of Marine & Atmospheric Science have published their findings in this week's issue of the Proceedings of the National Academy of Sciences, pointing to the need for rapid environmental assessments.

The environment in New Orleans and Lake Pontchartrain after Hurricanes Katrina and Rita showed high levels of contamination as floodwaters receded from the city, and this new study, titled "Impacts of Hurricanes Katrina and Rita on the Microbial Landscape of the New Orleans Area" provides new insights into public health and human exposure to both inhaled and ingested pathogens from sewage-contaminated floodwaters induced by hurricanes.

Rosenstiel School researchers from its NSF/NIEHS Center for Oceans and Human Health, along with five other universities and two other NSF/NIEHS Centers for Oceans and Human Health, analyzed water and sediment samples they collected as floodwaters receded from New Orleans during the two months after the 2005 hurricanes. The scientists collected water and sediment samples from the interior canal and shoreline of New Orleans and the offshore waters of Lake Pontchartrain, which showed higher than normal bacteria and pathogen levels. The bacteria and pathogens reduced to low levels within a few weeks after flooding had completely subsided.

"Our findings emphasize the importance of including environmental monitoring within disaster management plans," said Dr. Helena Solo-Gabriele, professor of environmental engineering at the University of Miami and co-author of the paper. "A rapid assessment of conditions can protect emergency workers and residents from potential illnesses that could result from exposure."

The 2005 events were characterized by an unusually high volume and long duration of human exposure. The most contaminated area tested near the Superdome contained high levels of sewage pathogens. Researchers pointed out monitoring efforts should focus on evaluating the impacts of sediments within the area since exposure to contaminated sediments, by inhaling or ingesting, could result in potential health risks. Efforts should include monitoring pathogens in addition to indicator microbes.

"We know that hurricanes bring infectious disease, chemical contamination and death in their wake," said Don Rice, director of NSF's chemical oceanography program, which funded the research. "Now we are making a concerted effort to study and understand the connections."

Sediment samples taken from the canal shoreline and from three homes showed elevated levels that could not be contributed solely to the effects of Hurricanes Katrina and Rita. The source of elevated bacteria levels in the canals and sediments appears to be the chronic discharge of contaminated water from the interior portions of the city.

Poor water quality, present prior to the hurricanes, was a major concern in the region, and efforts are needed in the region to improve the sanitary infrastructure.

Improvements should focus on the storm water drainage system in the region and reducing sewage contamination of groundwater seepage, researchers noted. No evidence of a long-term algal bloom was observed in New Orleans as a result of Hurricanes Katrina or Rita.