Virus Transport in the Subsurface

AbstractIn the United States alone, the estimated annual number of reported illnesses resulting from contact with waterborne pathogens was as low as one million and as high as seven million between 1971 and 1982, and 51% of all waterborne disease outbreaks due to the consumption of contaminated groundwater. It is estimated that approximately 20–25% of U.S. groundwater sources are contaminated with microbial pathogens, including more than 100 types of viruses. A literature review by Craun indicated that approximately one‐half of the surface water and groundwater sources tested contained enteric viruses. Even 9% of conventionally treated drinking water (coagulation, sedimentation, filtration, postfiltration disinfection using chlorine/ozone) tested positive for enteric viruses.Although water‐transmitted human pathogens include various bacteria, protozoa, helminths, and viruses, agents of major threat to human health are pathogenic protozoa (CryptosporidiumandGiardia) and enteroviruses. Despite ample information regarding the fate of viruses in the subsurface, research on the persistency of pathogenic protozoa through passage in soil and groundwater is just now emerging. In the past, it was generally believed that pathogenic protozoa are confined to surface water. Contrary to that expectation, recent monitoring results from 463 groundwater samples collected at 199 sites in 23 of the 48 contiguous states suggested that up to 50% of the groundwater sites were positive forCryptosporidium, Giardia, or both, depending on the parasite and the type of groundwater source (vertical wells, springs, infiltration galleries, and horizontal wells).